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125-467: The Emergency Alert System ( EAS ) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable , satellite and broadcast television and AM , FM and satellite radio. Informally, Emergency Alert System is sometimes conflated with its mobile phone counterpart Wireless Emergency Alerts (WEA),

250-413: A computer . All EAS equipment must be tested on a weekly basis. The required weekly test (RWT) consists, at a minimum, of the header and end-of-message tones. Though an RWT does not need an audio or graphic message announcing the test, many stations provide them as a courtesy to the public. In addition, television stations are not required to transmit a video message for weekly tests. RWTs are scheduled by

375-721: A WEA on all cell phones. The number of event types in the national system has grown to eighty. At first, all but three of the events (civil emergency message, immediate evacuation, and emergency action notification [national emergency]) were weather-related (such as a tornado warning ). Since then, several classes of non-weather emergencies have been added, including, in most states, the AMBER Alert System for child abduction emergencies. In 2016, three additional weather alert codes were authorized for use in relation to hurricane events, including Extreme Wind Warning (EWW), Storm Surge Warning (SSW) and Storm Surge Watch (SSA). In 2004,

500-550: A close approximation to UT1 , UTC occasionally has discontinuities where it changes from one linear function of TAI to another. These discontinuities take the form of leap seconds implemented by a UTC day of irregular length. Discontinuities in UTC occurred only at the end of June or December. However, there is provision for them to happen at the end of March and September as well as a second preference. The International Earth Rotation and Reference Systems Service (IERS) tracks and publishes

625-511: A different but related system. However, both the EAS and WEA, among other systems, are coordinated under the Integrated Public Alert and Warning System (IPAWS). The EAS, and more broadly IPAWS, allows federal, state, and local authorities to efficiently broadcast emergency alert and warning messages across multiple channels. The EAS became operational on January 1, 1997, after being approved by

750-453: A mean solar day in the mid‑19th century. In earlier centuries, the mean solar day was shorter than 86,400 SI seconds, and in more recent centuries it is longer than 86,400 seconds. Near the end of the 20th century, the length of the mean solar day (also known simply as "length of day" or "LOD") was approximately 86,400.0013 s. For this reason, UT is now "slower" than TAI by the difference (or "excess" LOD) of 1.3 ms/day. The excess of

875-418: A mean solar day to lengthen by one second (at a rate of 2 ms per century). This rate fluctuates within the range of 1.7–2.3 ms/cy. While the rate due to tidal friction alone is about 2.3 ms/cy, the uplift of Canada and Scandinavia by several metres since the last ice age has temporarily reduced this to 1.7 ms/cy over the last 2,700 years. The correct reason for leap seconds, then,

1000-474: A meridian drifting eastward faster and faster. Thus, the time system will lose its fixed connection to the geographic coordinates based on the IERS meridian . The difference between UTC and UT would reach 0.5 hours after the year 2600 and 6.5 hours around 4600. ITU-R Study Group 7 and Working Party 7A were unable to reach consensus on whether to advance the proposal to the 2012 Radiocommunications Assembly;

1125-545: A message. EEW capability is also required for all domestic cell phones sold after 2007. JMA also issues advisories regarding tropical cyclones in the western Pacific Ocean. Many countries in South America have a mechanism called " cadena nacional " ( Spanish : national broadcast ). It enables the leader of the country to address the people simultaneously on all TV channels and radio stations, interrupting normal programming. In some countries, such as Argentina and Venezuela,

1250-422: A minute is usually 60, but with an occasional leap second , it may be 61 or 59 instead. Thus, in the UTC time scale, the second and all smaller time units (millisecond, microsecond, etc.) are of constant duration, but the minute and all larger time units (hour, day, week, etc.) are of variable duration. Decisions to introduce a leap second are announced at least six months in advance in "Bulletin C" produced by

1375-463: A network of 77 radio stations that are, in coordination with FEMA, used to originate emergency alert and warning information to the public before, during, and after incidents and disasters. PEP stations are equipped with additional and backup communications equipment and power generators designed to enable them to continue broadcasting information to the public during and after an event. Beginning with WJR Detroit and WLW Cincinnati in 2016, FEMA began

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1500-441: A nine-minute warning (the resulting tornado would kill 23 people). The trend of cord cutting has led to concerns that viewers' lessened use of broadcast media in favor of streaming video services would inhibit their ability to receive emergency information (notwithstanding availability of alerts on mobile phones ). The READI Act called for an inquiry into the distribution of alerts via internet platforms. EAS equipment has been

1625-513: A particular time zone can be determined by adding or subtracting the number of hours and minutes specified by the UTC offset , which ranges from UTC−12:00 in the west to UTC+14:00 in the east (see List of UTC offsets ). The time zone using UTC is sometimes denoted UTC+00:00 or by the letter Z —a reference to the equivalent nautical time zone (GMT), which has been denoted by a Z since about 1950. Time zones were identified by successive letters of

1750-515: A pre-announced presidential speech, coverage of a national/local election, major local or national news coverage outside regularly scheduled newscast hours or a major national sporting event such as the Super Bowl or World Series , with other events such as the Indianapolis 500 and Olympic Games mentioned in individual EAS state plans. An RWT is not required during a calendar week in which an RMT

1875-545: A proposal by Pelmorex , owners of The Weather Network and MétéoMédia , to receive must-carry status for the channels, in exchange for developing a "national aggregator and distributor" of localized emergency alert messages compliant with the Common Alerting Protocol . The alert system, known as Alert Ready , built on a backend known as the National Alert Aggregation and Dissemination system (NAAD),

2000-662: A result of the International Telecommunication Union and the International Astronomical Union wanting to use the same abbreviation in all languages. The compromise that emerged was UTC , which conforms to the pattern for the abbreviations of the variants of Universal Time (UT0, UT1, UT2, UT1R, etc.). McCarthy described the origin of the abbreviation: In 1967 the CCIR adopted the names Coordinated Universal Time and Temps Universel Coordonné for

2125-547: A shift of the sun's movements relative to civil time, with the difference increasing quadratically with time (i.e., proportional to elapsed centuries squared). This is analogous to the shift of seasons relative to the yearly calendar that results from the calendar year not precisely matching the tropical year length. This would be a change in civil timekeeping, and would have a slow effect at first, but becoming drastic over several centuries. UTC (and TAI) would be more and more ahead of UT; it would coincide with local mean time along

2250-413: A source of error). UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time (summer time). For example, local time on the east coast of the United States is five hours behind UTC during winter, but four hours behind while daylight saving is observed there. In 1928, the term Universal Time ( UT ) was introduced by

2375-442: A standard clock not on the geoid, or in rapid motion, will not maintain synchronicity with UTC. Therefore, telemetry from clocks with a known relation to the geoid is used to provide UTC when required, on locations such as those of spacecraft. It is impossible to compute the exact time interval elapsed between two UTC timestamps without consulting a table showing how many leap seconds occurred during that interval. By extension, it

2500-551: A system could be implemented, and plans for further trials. However, no further trials or implementation of the system came. On 24 March 2020, the day after the UK went into a national lockdown in response to the COVID-19 pandemic , the government collaborated with the country's four main mobile networks , O2 , EE , Vodafone and Three , to send a text message alert regarding the new restrictions to all registered mobile phone numbers across

2625-799: A test flood alert was sent using the new technology to devices in Reading . Another generic test alert was sent to O2 customers on 11 May. Certain BT Mobile customers (with BT Mobile operating on the EE network) received two alerts on 20 May. A more public test of the system was carried out for devices in East Suffolk on 25 May, followed by a test across the UK on 12 June. Further limited tests were sent on 18 and 22 June. All of these test messages were sent specifically marked as operator test alerts, meaning that not all devices receive them. They are received by devices that have

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2750-482: A time standard. Amateur radio operators often schedule their radio contacts in UTC, because transmissions on some frequencies can be picked up in many time zones. UTC divides time into days, hours, minutes, and seconds . Days are conventionally identified using the Gregorian calendar , but Julian day numbers can also be used. Each day contains 24 hours and each hour contains 60 minutes. The number of seconds in

2875-420: A value to be chosen for the length of the atomic second that would accord with the celestial laws of motion. The coordination of time and frequency transmissions around the world began on 1 January 1960. UTC was first officially adopted in 1963 as CCIR Recommendation 374, Standard-Frequency and Time-Signal Emissions , and "UTC" became the official abbreviation of Coordinated Universal Time in 1967. In 1961,

3000-411: A warning signal in the event of a radiological emergency. Some emergencies ( AMBER Alerts , for instance) are also sent out via e-mail, cellphone text message, and highway signs. Many U.S. institutions of higher education now use multiple warning technologies on their campuses, including outdoor and indoor sirens, public address systems, email and cell phone text messaging, and digital displays. Prior to

3125-811: Is a national-level mobile risk alert and emergency communication system implemented by Intersec in partnership with the Ministry of the Interior in France. This system is designed to facilitate the efficient dissemination of critical alerts and safety information to citizens throughout the country. FR-Alert serves as a platform for delivering timely and accurate notifications related to various potential risks, including natural disasters and industrial incidents. Iranian armed forces texts are sent on several occasions. Also texts are sent by US just as well. The J-Alert system launched in 2007 aims to allow government officials to address

3250-448: Is affected by the leap seconds introduced in UTC). Time zones are usually defined as differing from UTC by an integer number of hours, although the laws of each jurisdiction would have to be consulted if sub-second accuracy was required. Several jurisdictions have established time zones that differ by an odd integer number of half-hours or quarter-hours from UT1 or UTC. Current civil time in

3375-532: Is an abbreviation for the time laboratory. The time of events may be provisionally recorded against one of these approximations; later corrections may be applied using the International Bureau of Weights and Measures (BIPM) monthly publication of tables of differences between canonical TAI/UTC and TAI( k )/UTC( k ) as estimated in real-time by participating laboratories. (See the article on International Atomic Time for details.) Because of time dilation ,

3500-478: Is approximately +1.7 ms per century. At the end of the 21st century, LOD will be roughly 86,400.004 s, requiring leap seconds every 250 days. Over several centuries, the frequency of leap seconds will become problematic. A change in the trend of the UT1 – UTC values was seen beginning around June 2019 in which instead of slowing down (with leap seconds to keep the difference between UT1 and UTC less than 0.9 seconds)

3625-485: Is not possible to compute the precise duration of a time interval that ends in the future and may encompass an unknown number of leap seconds (for example, the number of TAI seconds between "now" and 2099-12-31 23:59:59). Therefore, many scientific applications that require precise measurement of long (multi-year) intervals use TAI instead. TAI is also commonly used by systems that cannot handle leap seconds. GPS time always remains exactly 19 seconds behind TAI (neither system

3750-407: Is not the current difference between actual and nominal LOD, but rather the accumulation of this difference over a period of time: Near the end of the 20th century, this difference was about ⁠ 1 / 800 ⁠ of a second per day; therefore, after about 800 days, it accumulated to 1 second (and a leap second was then added). In the graph of DUT1 above, the excess of LOD above

3875-494: Is often activated when an unpredicted emergency such as a tornado, earthquake, or release of toxic gas happens. The vast majority of EAS alerts are generated by the National Weather Service . The Integrated Public Alert and Warning System (IPAWS) program of the U.S. Federal Emergency Management Agency is an attempt to integrate multiple public warning technologies into a coordinated nationwide "system of systems" using

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4000-515: Is repeated three times for redundancy. EAS decoders compare the received headers against one another, looking for an exact match between any two, eliminating most errors which can cause an activation to fail. The decoder then decides whether to ignore the message or to relay it on the air if the message applies to the local area served by the station (following parameters set by the broadcaster). The SAME header bursts are followed by an EAS attention tone, which lasts between 8 and 25 seconds, depending on

4125-456: Is responsible for the characteristic "screeching" or "chirping" sounds at the start and end of each message. The first signal is the "header" which encodes, among other information, the alert type and locations, or the specific area that should receive the message. The last short burst marks the end-of-message. These signals are read by specialized encoder-decoder equipment. This design allows for automated station-to-station relay of alerts to only

4250-568: Is scheduled. No testing has to be done during a calendar week in which all parts of the EAS (header burst, attention signal, audio message, and end of message burst) have been legitimately activated. In July 2018, in response to the aftermath of the false missile alert in Hawaii earlier in the year (which was caused by operator error during an internal drill protocol), the FCC announced that it would take steps to promote public awareness and improve efficiency of

4375-413: Is slightly longer than 86,400 SI seconds so occasionally the last minute of a UTC day is adjusted to have 61 seconds. The extra second is called a leap second. It accounts for the grand total of the extra length (about 2 milliseconds each) of all the mean solar days since the previous leap second. The last minute of a UTC day is permitted to contain 59 seconds to cover the remote possibility of

4500-441: Is the effective successor to Greenwich Mean Time (GMT) in everyday usage and common applications. In specialized domains such as scientific research, navigation, and timekeeping, other standards such as UT1 and International Atomic Time (TAI) are also used alongside UTC. UTC is based on TAI, which is a weighted average of hundreds of atomic clocks worldwide. UTC is within about one second of mean solar time at 0° longitude,

4625-630: Is the term that the International Early Warning Programme coordinated by the United Nations uses for all systems that are used to send emergency population warnings. ( IEWP 2007 ) The United Nations Development Programme uses the Send Word Now Emergency Notification System to alert its worldwide staff when an urgent situation arises. The Standard Emergency Warning Signal was originally adopted by

4750-534: Is to serve as a "last-ditch effort to get a message out if the president cannot get to the media", it can easily be made redundant by the immediate and constant coverage that major weather events and other newsworthy situations—such as, most prominently, the September 11 attacks in 2001—receive from television broadcasters and news channels . Following the attacks, then-FCC chairman Michael K. Powell cited "the ubiquitous media environment" as justification for not using

4875-463: Is very slowly decreasing because of tidal deceleration ; this increases the length of the mean solar day . The length of the SI ;second was calibrated on the basis of the second of ephemeris time and can now be seen to have a relationship with the mean solar day observed between 1750 and 1892, analysed by Simon Newcomb . As a result, the SI second is close to ⁠ 1 / 86400 ⁠ of

5000-570: The Bureau International de l'Heure began coordinating the UTC process internationally (but the name Coordinated Universal Time was not formally adopted by the International Astronomical Union until 1967). From then on, there were time steps every few months, and frequency changes at the end of each year. The jumps increased in size to 0.1 seconds. This UTC was intended to permit a very close approximation to UT2. In 1967,

5125-550: The Bureau of Meteorology in the 1970s for tropical cyclone warnings. It became a standard national emergency warning signal in 1995. It can be broadcast on radio, television, automated telephone calls and in some places by public address systems in the event of bushfire, flood, cyclone, tsunami, earthquake or terrorist attack. On June 11, 2009, the Canadian Radio-television and Telecommunications Commission (CRTC) approved

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5250-820: The Common Alerting Protocol . Systems targeted for inclusion in IPAWS include the Emergency Alert System , the Commercial Mobile Alert System using cellular telephones and other wireless devices and the NOAA Weather Radio network. Many states use existing air raid sirens to warn of tornadoes and flash floods. People living near certain nuclear facilities such as the Hanford Site in Washington have special radios in their home that are set to broadcast

5375-647: The Federal Communications Commission (FCC) and the National Oceanic and Atmospheric Administration (NOAA). The EAS regulations and standards are governed by the Public Safety and Homeland Security Bureau of the FCC . All broadcast television, broadcast and satellite radio stations, as well as multichannel video programming distributors (MVPDs), are required to participate in the system. Messages in

5500-589: The Federal Communications Commission (FCC) in November 1994, replacing the Emergency Broadcast System (EBS), and largely supplanted Local Access Alert systems, though Local Access Alert systems are still used from time to time. Its main improvement over the EBS, and perhaps its most distinctive feature, is its application of a digitally encoded audio signal known as Specific Area Message Encoding (SAME), which

5625-558: The International Earth Rotation and Reference Systems Service . The leap seconds cannot be predicted far in advance due to the unpredictable rate of the rotation of Earth. Nearly all UTC days contain exactly 86,400 SI seconds with exactly 60 seconds in each minute. UTC is within about one second of mean solar time (such as UT1 ) at 0° longitude , (at the IERS Reference Meridian ). The mean solar day

5750-537: The SI second was redefined in terms of the frequency supplied by a caesium atomic clock. The length of second so defined was practically equal to the second of ephemeris time. This was the frequency that had been provisionally used in TAI since 1958. It was soon decided that having two types of second with different lengths, namely the UTC second and the SI second used in TAI, was a bad idea. It

5875-497: The September 11 attacks , has been credited to making usage of the system unnecessary or redundant. In practice, it is used at a regional scale to distribute information regarding imminent threats to public safety, such as severe weather situations (including flash floods and tornadoes ), AMBER Alerts , and other civil emergencies. It is jointly coordinated by the Federal Emergency Management Agency (FEMA),

6000-920: The UT1 variant of universal time . See the " Current number of leap seconds " section for the number of leap seconds inserted to date. The first leap second occurred on 30 June 1972. Since then, leap seconds have occurred on average about once every 19 months, always on 30 June or 31 December. As of July 2022 , there have been 27 leap seconds in total, all positive, putting UTC 37 seconds behind TAI. A study published in March 2024 in Nature concluded that accelerated melting of ice in Greenland and Antarctica due to climate change has decreased Earth's rotational velocity, affecting UTC adjustments and causing problems for computer networks that rely on UTC. Earth's rotational speed

6125-604: The WWV time signals, named for the shortwave radio station that broadcasts them. In 1960, the U.S. Naval Observatory, the Royal Greenwich Observatory, and the UK National Physical Laboratory coordinated their radio broadcasts so that time steps and frequency changes were coordinated, and the resulting time scale was informally referred to as "Coordinated Universal Time". In a controversial decision,

6250-509: The " four-minute warning ". Its purpose was to warn the population, through a combination of air-raid sirens and messages over television and radio, of an impending nuclear missile attack from the Soviet Union ; its name derived from the expected amount of time between knowledge of the strike and the missile landing. The system was dismantled following the dissolution of the Soviet Union and

6375-575: The 25th century, four leap seconds are projected to be required every year, so the current quarterly options would be insufficient. In April 2001, Rob Seaman of the National Optical Astronomy Observatory proposed that leap seconds be allowed to be added monthly rather than twice yearly. In 2022 a resolution was adopted by the General Conference on Weights and Measures to redefine UTC and abolish leap seconds, but keep

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6500-560: The Cabinet Office posting notices on social media, as well as some mobile networks. Further operator tests were carried out throughout July, August and September. The sound they use is exactly the same as the one in the US, some phones will beep three times before the message is read out, whilst other phones will signal a pattern for 10 seconds. There is no mention if alerts would be broadcast on TV or radio. The government initially planned to make

6625-599: The DUT1 correction (UT1 − UTC) for applications requiring a closer approximation of UT1 than UTC now provided. The current version of UTC is defined by International Telecommunication Union Recommendation (ITU-R TF.460-6), Standard-frequency and time-signal emissions , and is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the accumulated difference between TAI and time measured by Earth's rotation . Leap seconds are inserted as necessary to keep UTC within 0.9 seconds of

6750-413: The EAS are composed of four parts: a digitally encoded Specific Area Message Encoding (SAME) header , an attention signal, an audio announcement, and a digitally encoded end-of-message marker. The SAME header is the most critical part of the EAS design. It contains information about who originated the alert (the president, state or local authorities, the National Weather Service (NOAA/NWS), or

6875-541: The EAS in their immediate aftermath. Glenn Collins of The New York Times acknowledged these limitations, noting that "no president has ever used the current [EAS] system or its technical predecessors in the last 50 years, despite the Soviet missile crisis , a presidential assassination , the Oklahoma City bombing , major earthquakes and three recent high-alert terrorist warnings", and that using it would have actually hindered

7000-463: The EAS, as well as all cable and satellite services in the United States. They are not relayed on the NOAA Weather Radio (NOAA/NWS) network as it is an initiation-only network and does not receive messages from the PEP network. The national test would transmit and relay an Emergency Action Notification on November 9, 2011 at 2:00 p.m. EST. The Federal Communications Commission found that only half of

7125-501: The EBS, the attention signal is followed by a voice message describing the details of the alert. The message ends with 3 bursts of the AFSK "EOM", or End of Message , which is the text NNNN , preceded each time by the binary 10101011 calibration. Under a 2006 executive order issued by George W. Bush , the U.S. government was instructed to create "an effective, reliable, integrated, flexible, and comprehensive" public warning system. This

7250-505: The Earth rotating faster, but that has not yet been necessary. The irregular day lengths mean fractional Julian days do not work properly with UTC. Since 1972, UTC may be calculated by subtracting the accumulated leap seconds from International Atomic Time (TAI), which is a coordinate time scale tracking notional proper time on the rotating surface of the Earth (the geoid ). In order to maintain

7375-547: The Earth's rotation has sped up, causing this difference to increase. If the trend continues, a negative leap second may be required, which has not been used before. This may not be needed until 2025. Some time in the 22nd century, two leap seconds will be required every year. The current practice of only allowing leap seconds in June and December will be insufficient to maintain a difference of less than 1 second, and it might be decided to introduce leap seconds in March and September. In

7500-532: The Emergency Action Notification) is the notice to broadcasters that the president of the United States or their designee will deliver a message over the EAS via the PEP system. The government has stated that the system would allow a president to speak during a national emergency within 10 minutes. The National Public Warning System, also known as the Primary Entry Point ( PEP ) stations, is

7625-581: The Emergency Alert System", and acts as an emergency presidential link into the EAS. The FNARS net control station is located at the Mount Weather Emergency Operations Center . Once an EAN is received by an EAS participant from a PEP station (or any other participant) the message then "daisy chains ' " through the network of participants. "Daisy chains" form when one station receives a message from multiple other stations and

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7750-507: The English and French names with the acronym UTC to be used in both languages. The name "Coordinated Universal Time (UTC)" was approved by a resolution of IAU Commissions 4 and 31 at the 13th General Assembly in 1967 (Trans. IAU, 1968). Time zones around the world are expressed using positive, zero, or negative offsets from UTC , as in the list of time zones by UTC offset . The westernmost time zone uses UTC−12 , being twelve hours behind UTC;

7875-457: The FCC issued a Notice of Proposed Rulemaking (NPR) seeking comment on whether EAS in its present form is the most effective mechanism for warning the American public of an emergency and, if not, on how EAS can be improved, such as mandatory text messages to cellphones, regardless of subscription. As noted above, rules implemented by the FCC on July 12, 2007 provisionally endorse incorporating CAP with

8000-498: The FCC issued a notice of proposed rulemaking seeking to prioritize the display of alert audio and text from CAP messages, in order to provide higher quality alert audio, improve parity between the visual display and audio for the benefit of the hearing impaired , and to reduce the amount of technical jargon contained within the visual display. The rules were enacted in September 2022, with a deadline of December 12, 2023, for compliance;

8125-473: The FCC later granted an extension to some broadcasters due to a delay in the release of associated software updates by EAS decoder vendor Sage. The FCC requires all broadcast stations and multichannel video programming distributors (MVPD), hereafter "EAS participants", to install and maintain FCC-certified EAS decoders and encoders at their control points or headends . These decoders continuously monitor

8250-468: The FCC stated that future national tests would be delivered under the new event code "National Periodic Test" ("NPT"), and list "United States" as its location. A second national test, the first classified as an NPT, occurred on September 28, 2016 as part of National Preparedness Month . A third national periodic test occurred on September 27, 2017. The fourth NPT occurred on October 3, 2018 (delayed from September 20, 2018, due to Hurricane Florence ). It

8375-540: The International Astronomical Union to refer to GMT, with the day starting at midnight. Until the 1950s, broadcast time signals were based on UT, and hence on the rotation of the Earth. In 1955, the caesium atomic clock was invented. This provided a form of timekeeping that was both more stable and more convenient than astronomical observations. In 1956, the U.S.  National Bureau of Standards and U.S. Naval Observatory started to develop atomic frequency time scales; by 1959, these time scales were used in generating

8500-503: The LOD over the nominal 86,400 s accumulates over time, causing the UTC day, initially synchronised with the mean sun, to become desynchronised and run ahead of it. Near the end of the 20th century, with the LOD at 1.3 ms above the nominal value, UTC ran faster than UT by 1.3 ms per day, getting a second ahead roughly every 800 days. Thus, leap seconds were inserted at approximately this interval, retarding UTC to keep it synchronised in

8625-575: The National Periodic Test, which last occurred on October 4, 2023. Universal Coordinated Time This is an accepted version of this page Coordinated Universal Time ( UTC ) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones . UTC facilitates international communication, navigation, scientific research, and commerce. UTC has been widely embraced by most countries and

8750-677: The SAME protocol. In November 2020, Congress passed the Reliable Emergency Alert Distribution Improvement (READI) Act. First sponsored by Hawaii Senator Brian Schatz in response to the Hawaii false missile alert , it amends the Warning, Alert, and Response Network (WARN) Act to require distribution of wireless alerts issued by the administrator of FEMA, and commands the FCC to establish a means of reporting false alerts, encourage

8875-450: The UK. In order to not overwhelm the networks, the operators sent the messages in batches, going to one million or so numbers at a time. This process took over 24 hours, with some people not receiving the message until the following day. The government was accused of ignoring its own advice from the 2013 trials to set up a dedicated public alert system. In response, it began developing a system using Cell Broadcast technology. In March 2021,

9000-455: The UTC second equal to the TAI second. This CCIR Recommendation 460 "stated that (a) carrier frequencies and time intervals should be maintained constant and should correspond to the definition of the SI second ; (b) step adjustments, when necessary, should be exactly 1 s to maintain approximate agreement with Universal Time (UT); and (c) standard signals should contain information on the difference between UTC and UT." As an intermediate step at

9125-561: The UTC system. If only milliseconds precision is needed, clients can obtain the current UTC from a number of official internet UTC servers. For sub-microsecond precision, clients can obtain the time from satellite signals. UTC is also the time standard used in aviation , e.g. for flight plans and air traffic control . In this context it is frequently referred to as Zulu time, as described below. Weather forecasts and maps all use UTC to avoid confusion about time zones and daylight saving time. The International Space Station also uses UTC as

9250-413: The adoption of the Emergency Alert System, the United States used CONELRAD from 1951 to 1963 and the Emergency Broadcast System from 1963 to 1997. Cable television systems in the United States also have emergency warnings at the time, known as Local Access Alert or Emergency Override System . A notable example of an emergency alert being issued in the United States was a nationwide alert test, known as

9375-526: The aftermath of the disaster. Since its inception in 2012 and through its official implementation in 2017 onwards, it has been used to provide alerts and information regarding natural disasters such as floods, wildfires, tsunami and earthquake warnings. All cell phones on sale in the country are required by law to be compatible with the SAE system since 2017. Between 1953 and 1992, the UK government had an alert system known as

9500-439: The air-raid siren network ( défense passive ) developed before World War II . It consists of about 4,500 electronic or electromechanical sirens placed all over France. In some cases, the warning signal may be played by a mobile system installed on the fire department 's vehicles. The warning signal is described by décret ( by law ) of March 23, 2007. It consists in a modulated sound going up and down (up to 380 Hz) during

9625-482: The alerts. The alert was received by most mobile phones between 14:59 and 15:05 BST, however some mobile devices on the Three network did not receive the alert. The bulk of emergency warnings in the United States are sent through the Emergency Alert System , implemented in 1997. The EAS can be activated by national, state, regional, or local authorities, including police, fire, weather, and other governmental authorities. EAS

9750-551: The alphabet and the Greenwich time zone was marked by a Z as it was the point of origin. The letter also refers to the "zone description" of zero hours, which has been used since 1920 (see time zone history ). Since the NATO phonetic alphabet word for Z is "Zulu", UTC is sometimes known as "Zulu time". This is especially true in aviation, where "Zulu" is the universal standard. This ensures that all pilots, regardless of location, are using

9875-526: The area the alert was intended for. Like the Emergency Broadcast System, the system is primarily designed to allow the President of the United States to address the country via all radio and television stations in the event of a national emergency. Despite this, neither the system nor its predecessors have been used in this manner. The ubiquity of news coverage in these situations, such as during

10000-400: The audio portion of an EAS message to utilize higher quality digital audio , rather than needing to carry the audio off-air from the originating station. Under an FCC report and order issued in 2007, EAS participants would be required to migrate to digital equipment supporting CAP within 180 days of the specification's adoption by FEMA. This was originally scheduled for September 30, 2010, but

10125-434: The audio, and (where applicable) a visual display containing the extended text, from the associated CAP message. EAS participants are required to keep logs of all received messages. Logs may be kept by hand but are usually kept automatically by a small receipt printer in the encoder/decoder unit. Logs may also be kept electronically inside the unit as long as there is access to an external printer or method to transfer them to

10250-448: The availability of live coverage from media outlets. Following the tornado outbreak of March 3, 2019 , Birmingham, Alabama NWS meteorologist Kevin Laws told CNN that he, personally, wished that alerts could be updated in real-time in order to reflect the unpredictable nature of weather events, noting that the storm system's unexpected change in trajectory towards Lee County resulted in only

10375-408: The broadcast of these messages is obligatory. Many of these systems were created by past military governments, and political use of the mechanism is common. The SAE (Spanish: Sistema de Alerta de Emergencia; English: Emergency Alert System) was created as a response to the 2010 Chilean Earthquake after the failure by the national authorities to provide safety precautions and speedy information during

10500-600: The broadcaster), a short, general description of the event (tornado, flood, severe thunderstorm), the areas affected (up to 32 counties or states), the expected duration of the event (in minutes), the date and time it was issued (in UTC ), and an identification of the originating station. There are 79 radio stations designated as National Primary Stations in the Primary Entry Point (PEP) System to distribute presidential messages to other broadcast stations and cable systems. The National Emergency Message (formerly known as

10625-544: The chairman of Study Group 7 elected to advance the question to the 2012 Radiocommunications Assembly (20 January 2012), but consideration of the proposal was postponed by the ITU until the World Radio Conference in 2015. This conference, in turn, considered the question, but no permanent decision was reached; it only chose to engage in further study with the goal of reconsideration in 2023. A proposed alternative to

10750-441: The civil second constant and equal to the SI second, so that sundials would slowly get further and further out of sync with civil time. The leap seconds will be eliminated by 2035. The resolution does not break the connection between UTC and UT1, but increases the maximum allowable difference. The details of what the maximum difference will be and how corrections will be implemented is left for future discussions. This will result in

10875-551: The currently used prime meridian , and is not adjusted for daylight saving time . The coordination of time and frequency transmissions around the world began on 1 January 1960. UTC was first officially adopted as a standard in 1963 and "UTC" became the official abbreviation of Coordinated Universal Time in 1967. The current version of UTC is defined by the International Telecommunication Union . Since adoption, UTC has been adjusted several times, notably adding leap seconds in 1972. Recent years have seen significant developments in

11000-465: The deadline was later delayed to June 30, 2012 at the request of broadcasters. The FCC has established that IPAWS is not a full substitute for the SAME protocol, as it is vulnerable to situations that may make internet connectivity unavailable. Therefore, as a backup distribution path, broadcasters must also convert CAP messages to SAME headers to enable backwards compatibility with the existing "daisy chain" method of EAS distribution. In December 2021,

11125-473: The difference between UTC and Universal Time, DUT1 = UT1 − UTC, and introduces discontinuities into UTC to keep DUT1 in the interval (−0.9 s, +0.9 s). As with TAI, UTC is only known with the highest precision in retrospect. Users who require an approximation in real time must obtain it from a time laboratory, which disseminates an approximation using techniques such as GPS or radio time signals . Such approximations are designated UTC( k ), where k

11250-541: The easternmost time zone uses UTC+14 , being fourteen hours ahead of UTC. In 1995, the island nation of Kiribati moved those of its atolls in the Line Islands from UTC−10 to UTC+14 so that Kiribati would all be on the same day. UTC is used in many Internet and World Wide Web standards. The Network Time Protocol (NTP), designed to synchronise the clocks of computers over the Internet, transmits time information from

11375-483: The end of 1971, there was a final irregular jump of exactly 0.107758 TAI seconds, making the total of all the small time steps and frequency shifts in UTC or TAI during 1958–1971 exactly ten seconds, so that 1 January 1972 00:00:00 UTC was 1 January 1972 00:00:10 TAI exactly, and a whole number of seconds thereafter. At the same time, the tick rate of UTC was changed to exactly match TAI. UTC also started to track UT1 rather than UT2. Some time signals started to broadcast

11500-449: The end of the Cold War . In 2013, the government conducted trials of a public alert system using both SMS messaging and Cell Broadcast technology to send alert messages to mobile devices in areas affected by an emergency. A report was published in 2014 that said the trials were successful and that 85% of people thought that such a system would be a good idea, as well as detailing how such

11625-434: The establishment of State Emergency Communications Committees (SECC) that would meet annually to evaluate their EAS plans, require the repetition of alerts surrounding "emergencies of national significance", and open an inquiry into the feasibility of implementing the EAS on internet-related services. The EAS can only be used to relay audio messages that preempt all programming; as the intent of an Emergency Action Notification

11750-585: The first minute, and repeated three times. The end of alert is a continuous signal lasting 30 seconds. The system is tested the first Wednesday of every month at 11.45 in the north, 12.00 in the center, and at 12.15 in the south; for tests, the modulated signal is played only once. When the warning signal sounds, people are expected to remain at home or the building they are in and listen to further instructions on radio via France Info , France Inter , or local stations. Instructions may also be announced by police or fire department vehicles. FR-Alert FR-Alert

11875-509: The frequency for the caesium transition , newly established, with the ephemeris second . The ephemeris second is a unit in the system of time that, when used as the independent variable in the laws of motion that govern the movement of the planets and moons in the solar system, enables the laws of motion to accurately predict the observed positions of solar system bodies. Within the limits of observable accuracy, ephemeris seconds are of constant length, as are atomic seconds. This publication allowed

12000-399: The frequency of the signals was initially set to match the rate of UT, but then kept at the same frequency by the use of atomic clocks and deliberately allowed to drift away from UT. When the divergence grew significantly, the signal was phase shifted (stepped) by 20 ms to bring it back into agreement with UT. Twenty-nine such steps were used before 1960. In 1958, data was published linking

12125-431: The integrity of the system, and prevent false activations, the FCC prohibits the use of actual or simulated EAS/WEA tones and attention signals outside of genuine alerts, tests, or authorized public service announcements , especially when they are used "to capture audience attention during advertisements; dramatic, entertainment, and educational programs" (even if the footage is documentation of an event where an actual alert

12250-529: The internet cannot be used. The sixth NPT was postponed to 2021 amid the ongoing COVID-19 pandemic "out of consideration for the unusual circumstances and working conditions for those in the broadcast and cable industry." The sixth test occurred on August 11, 2021, at 2:20 pm EDT. This test involved the WEA system alongside television and radio. As of 2022, as part of a clarification and streamlining of terminology used in messages, further NPTs will now be referred to in

12375-435: The long term. The actual rotational period varies on unpredictable factors such as tectonic motion and has to be observed, rather than computed. Just as adding a leap day every four years does not mean the year is getting longer by one day every four years, the insertion of a leap second every 800 days does not indicate that the mean solar day is getting longer by a second every 800 days. It will take about 50,000 years for

12500-494: The nominal 86,400 s corresponds to the downward slope of the graph between vertical segments. (The slope became shallower in the 1980s, 2000s and late 2010s to 2020s because of slight accelerations of Earth's rotation temporarily shortening the day.) Vertical position on the graph corresponds to the accumulation of this difference over time, and the vertical segments correspond to leap seconds introduced to match this accumulated difference. Leap seconds are timed to keep DUT1 within

12625-461: The option to receive test alerts turned on in the device settings, and some devices do not have this option. The first test alert marked as an actual alert, meaning it will be received by all compatible devices in the given area, was sent on 29 June, again only to devices in Reading. Because this alert would be received by most mobile devices in the Reading area, this alert was given more publicity, with

12750-403: The originating station. The tone is 1,050 Hz on a NOAA Weather Radio station. On commercial broadcast stations, a "two-tone" attention signal of 853  Hz and 960 Hz sine waves is used instead, the same signal used by the older Emergency Broadcast System . These tones have become infamous, and can be considered both frightening and annoying by listeners; in fact,

12875-474: The participants received the message via Integrated Public Alert and Warning System , and some "failed to receive or retransmit alerts due to erroneous equipment configuration, equipment readiness and upkeep issues, and confusion regarding EAS rules and technical requirements", and that participation among low-power broadcasters was low. Many reported visuals or audio missing, and in the case of DirecTV , hearing Lady Gaga music instead. To reduce viewer confusion,

13000-503: The population directly via loudspeakers. It aims to cover earthquake, tsunami, volcano, and military emergencies. The Earthquake Early Warning system is operated by the Japan Meteorological Agency . It is capable of delivering warnings a few seconds before S-waves can propagate to distant locations. Warnings are broadcast by radio and television stations, and compatible equipment can automatically turn on when receiving

13125-552: The process of constructing transportable studio shelters at the transmitters of 33 PEP stations, which feature broadcasting equipment, emergency provisions, a rest area, and an air filtration system. NPWS project manager Manny Centeno explained that these shelters were designed to "[expand] the survivability of these stations to include an all hazards platform, which means chemical, biological, radiological air protection and protection from electromagnetic pulse." The FEMA National Radio System (FNARS) "Provides Primary Entry Point service to

13250-527: The provincial government, county authorities, tribal government agencies, Environment Canada , and the Royal Canadian Mounted Police . CKUA developed and maintained the EPWS until January 2010, when it lost a bid to modernize the system to an outside vendor (the contract had provided 15% of the station's overall budget). In June 2011, an updated version of the system known as Alberta Emergency Alert

13375-416: The realm of UTC, particularly in discussions about eliminating leap seconds from the timekeeping system because leap seconds occasionally disrupt timekeeping systems worldwide. The General Conference on Weights and Measures adopted a resolution to alter UTC with a new system that would eliminate leap seconds by 2035. The official abbreviation for Coordinated Universal Time is UTC . This abbreviation comes as

13500-629: The same 24-hour clock , thus avoiding confusion when flying between time zones. See the list of military time zones for letters used in addition to Z in qualifying time zones other than Greenwich. On electronic devices which only allow the time zone to be configured using maps or city names, UTC can be selected indirectly by selecting cities such as Accra in Ghana or Reykjavík in Iceland as they are always on UTC and do not currently use daylight saving time (which Greenwich and London do, and so could be

13625-841: The signals from other nearby broadcast stations for EAS messages. For reliability, at least two source stations must be monitored, one of which must be a designated local primary . Participants are to retain the latest version of the EAS handbook. EAS participants are required by federal law to relay National Emergency Messages (EAN, formerly Emergency Action Notification) immediately (47 CFR Part 11.54). Broadcasters traditionally have been allowed to opt out of relaying other alerts such as severe weather , and child abduction emergencies ( AMBER Alerts ) if they so choose. In practice, television stations with local news departments will usually interrupt regularly-scheduled programming during newsworthy situations (such as severe weather) to provide extended coverage. If possible, EAS participants must transmit

13750-772: The station on random days and times, (though quite often during late night or early afternoon hours), and are generally not relayed. Required monthly tests (RMTs) are generally originated by the local or state primary station, a state emergency management agency, or by the National Weather Service and are then relayed by broadcast stations and cable channels. RMTs must be performed between 8:30 a.m. and local sunset during odd numbered months, and between local sunset and 8:30 a.m. during even numbered months. Received monthly tests must be retransmitted within 60 minutes of receipt. Additionally, an RMT should not be scheduled or conducted during an event of great importance such as

13875-400: The station then forwards that message to multiple other stations. This process creates many redundant paths through which the message may flow increasing the likelihood that the message will be received by all participants and adding to the survivability of the system. Each EAS participant is required to monitor at least two other participants. Because the header lacks error detection codes, it

14000-459: The subject of various cyberattacks , caused primarily by participants using insecure or factory default passwords on their encoders and decoders, and outdated software containing unpatched vulnerabilities . On multiple occasions, federal government departments have warned that failure to employ secure passwords and keep software updated made EAS equipment vulnerable to such attacks, which could result in disruptions such as false alerts. To protect

14125-550: The system fully live and functional in the summer of 2021, but this was later changed to autumn of 2021, and then again delayed to early 2022 and then the summer 2022, with a publicised nationwide alert sent to all devices to demonstrate the system. A nationwide test of the system took place at 15:00 BST on the 23rd April 2023. Alerts were received by all mobile devices connected to 4G and 5G networks, running Android 11 or later or iOS 14.5 or later. Some older Android devices, as well as other makes and models of phones, also received

14250-453: The system, including requiring safeguards to prevent distribution of false alarms, the ability to authorize "live code" tests—which would simulate the process and response to an actual emergency, and authorizations to use the EAS tones in public service announcements that promote awareness of the system. On February 3, 2011, the FCC announced plans and procedures for national EAS tests, which involve all television and radio stations connected to

14375-527: The test message as a "Nationwide Test of the Emergency Alert System" issued by the United States Government . On May 3, 2022, it was announced that the seventh NPT would not take place during 2022, and instead occur in early 2023. On August 3, 2023, FEMA and the FCC announced that the seventh NPT would occur October 4, 2023 with a backup date of October 11, 2023. The test commenced just before 2:20 pm ET, and consisted of an alert on TV/radio as well as

14500-429: The two tones, which form approximately the interval of a just major second at an unusually high pitch, were chosen specifically for their ability to draw attention, due to their unpleasantness on the human ear . The SAME header is equally known for its shrillness, which many have found to be startling. The "two-tone" system is no longer required as of 1998, and is to be used only for audio alerts before EAS messages. Like

14625-489: The vertical range depicted by the adjacent graph. The frequency of leap seconds therefore corresponds to the slope of the diagonal graph segments, and thus to the excess LOD. Time periods when the slope reverses direction (slopes upwards, not the vertical segments) are times when the excess LOD is negative, that is, when the LOD is below 86,400 s. As the Earth's rotation continues to slow, positive leap seconds will be required more frequently. The long-term rate of change of LOD

14750-495: Was accomplished via expansions to the aforementioned PEP network, and the development of the Integrated Public Alert and Warning System (IPAWS)—a national aggregator and distributor of alert information using the XML -based Common Alerting Protocol (CAP) and an internet network. IPAWS can be used to distribute alert information to EAS participants, supported mobile phones ( Wireless Emergency Alerts ), and other platforms. IPAWS also allows

14875-408: Was also dissatisfaction with the frequent jumps in UTC (and SAT). In 1968, Louis Essen , the inventor of the caesium atomic clock, and G. M. R. Winkler both independently proposed that steps should be of 1 second only. to simplify future adjustments. This system was eventually approved as leap seconds in a new UTC in 1970 and implemented in 1972, along with the idea of maintaining

15000-571: Was first established in 2010, and further expanded as a result of consultation with government officials, broadcasters, and the CRTC. In August 2014, the CRTC ruled that all television stations, radio stations, and broadcast distribution undertakings had to begin mandatory carriage of local alerts relayed through NAAD by March 31, 2015. The province of Alberta had its own system called the Emergency Public Warning System (EPWS). The EPWS

15125-454: Was introduced, which emphasized multi-platform availability of alerts and advisories on digital platforms, such as online and through a mobile app . Participation in AEA is now considered mandatory under the CRTC's national public alerting mandate. In France, the population warning is made via air raid siren . This network is called the "Réseau national d'alerte" (RNA). The system is inherited from

15250-817: Was issued). Broadcasters who misuse the tones may be sanctioned (including being required to partake in compliance measures) and fined. In an opposite move, in 2013 the FCC granted a one-year waiver for a PSA pertaining to the Wireless Emergency Alerts system, with assurance that the tones used in the PSA contained a different set of codes designed not to activate EAS receivers. Emergency population warning Many local areas use emergency population warnings to advise of prison escapes , abducted children , emergency telephone number outages, and other events. In order to develop an effective emergency warning system, certain things are required: Early warning system

15375-457: Was preceded by the first mandatory wireless emergency alert test. The fifth NPT occurred on August 7, 2019, and moved up from past years to prevent it from occurring during the heart of the Atlantic hurricane season . The test focused exclusively on distribution to broadcast outlets and television providers via the primary entry point network to gauge the efficiency of alert distribution in the event

15500-556: Was put into place after a major tornado swept through the city of Edmonton in 1987, killing 27 and causing millions of dollars in damage. Unlike the American EAS, however, broadcast of the EPWS was not mandatory on radio and television stations. It was broadcast on the CKUA Radio Network and was televised on CTV Two Alberta and other participating stations. EPWS warnings could be initiated by municipal police and fire departments,

15625-408: Was thought better for time signals to maintain a consistent frequency, and that this frequency should match the SI second. Thus it would be necessary to rely on time steps alone to maintain the approximation of UT. This was tried experimentally in a service known as "Stepped Atomic Time" (SAT), which ticked at the same rate as TAI and used jumps of 0.2 seconds to stay synchronised with UT2. There

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