Portugal has two time zones and observes daylight saving time. Continental Portugal and Madeira use UTC+00:00, while the Azores use UTC–01:00. Daylight saving time (locally known as Hora de Verão, meaning "summer time") is observed nationwide from the last Sunday in March to the last Sunday in October, when continental Portugal and Madeira advances one hour to UTC+01:00, and the Azores advances one hour to UTC+00:00. [1]
In the early 19th century, Portugal adopted mean solar time. [2] Navy (located in Lisbon) and Coimbra Astronomical Observatories calculated solar time to be used as legal time in their longitude regions. [2] In 1861, the Astronomical Observatory of Lisbon was founded and, in 1878, it was tasked with the exclusive competence of calculate its mean solar time and to transmit it to rest of the country’s public services. [2] Thus, in practice, Portuguese standard time was defined as the mean solar time at Lisbon Observatory longitude, which was later calculated as being GMT–00:36:45. [3]
In 1911, it was agreed that standard time in Portugal should be defined in accordance with the 1884 prime meridian system. [4] By the Decree of 26 May 1911, a reform was approved regarding standard time in Portugal and in its overseas Empire: although almost all continental Portugal is located west of the 7.5°W meridian (i.e. in the theoretical zone of UTC-01:00 time zone), mainland Portugal adopted UTC+00:00 as its time zone. [4] By the same law, UTC-02:00 time zone was adopted for the Azores and Cape Verde, UTC-01:00 for Madeira and Portuguese Guinea, UTC+00:00 for São Tomé and Príncipe and São João Baptista de Ajudá, UTC+01:00 for Angola, UTC+02:00 for Mozambique, UTC+05:00 for Portuguese India and UTC+08:00 for Macau and Portuguese Timor. [4] These time zones were adopted on 1 January 1912. [4]
Daylight saving time (Hora de Verão, or "summer time", in Portuguese) was observed for the first time in 1916, during World War I, and it consisted in advancing clocks by one hour. [2] [3] [5] In that year, DST was observed from 17 June to 1 November but in following years until 1921, it was observed from 1 June to 14 October. [2] [3]
DST continued to be observed every year in 1920s and 1930s, although some small interruptions had occurred (1922–1923, 1925, 1930 and 1933), as well as the start and end date of DST, which often varied. [3]
Between 1942 and 1945, during World War II, Portugal not only advanced clocks by one hour during DST, as also advanced them by another hour during some months of those years, coming to have clocks two hours ahead of GMT, effectively observing "double DST". [3] Portugal returned to GMT following the end of the war in 1945, and one hour of DST continued to be observed. [3] In 1948, it was approved that DST should be observed from the first Sunday in April to the first Sunday in October. [6]
From 1966, DST was observed year-round, so that, in practice, Portugal changed its time zone from WET (UTC+00:00) to CET (UTC+01:00). [3] [7] However, due to the later sunrises and sunsets, many complaints accumulated: on winter mornings, people went to work under a completely dark sky, and at 09:00, when school classes started, the sun was still rising, which eventually had repercussions on students' school performance and their safety during morning trips from home to school. [8] Furthermore, in the 1970s, the idea of reintroducing DST as an energy saving measure gained strength in Europe as well as in Portugal. [9] However, although there were so many complaints in the country with the use of UTC+01:00 year round, it became clear to policymakers that if DST was to be re-introduced, it could never be observed as CEST (UTC+02:00), and the only solution was to re-adopt WET as standard time. Therefore, Portugal re-adopted Western European Time (UTC+00:00) as its standard time in 1976. [8] DST started to be observed every year as WEST (UTC+01:00), usually from early April to later September. [3] [8] From 1981 on, DST started to be observed from the last Sunday in March to the last Sunday in September. [3]
In 1986, time in Portugal began to be calculated in accordance with UTC rather than GMT. [2] [10]
In 1992, during the government of Aníbal Cavaco Silva, by Decree-Law 124/92, mainland Portugal officially changed its time zone from Western European Time to Central European Time. [3] [11] Unlike the 1966 change to CET, DST was observed as Central European Summer Time (UTC+02:00), from the last Sunday in March to the last Sunday in September. [3] [11] The measure, approved without the consultation of Lisbon Observatory, had the intention of promoting energy savings, in order that "Portugal follow, in work schedules, the countries with which it maintains more frequent contacts" (DL 124/92) and so promoting economic growth. [11] However, the measure quickly proved to be a failure in achieving its objectives and became unpopular: on winter mornings, the sun was still rising at 09:00 and people travelled to work in the dark. [12] [13] Children also began the school day in darkness, with repercussions on their standards of learning, school performance and sleeping habits. [13] [14] [15] It was even common that children fell asleep in the early morning classes. [12] [15] On summer evenings, the usage of Central European Summer Time was revealed to have a disturbing effect on peoples', especially children's, sleeping habits, as the sun was still setting as late as 22:30, so the sky was only completely dark towards midnight. [12] [15] [14] A company hired by European Commission conducted a study which concluded that, in fact, there were no energy savings because, due to the dark early mornings, workers turned on lights in their offices and forgot to turn them off, leaving them switched on for the rest of the morning, which increased energy consumption. [13] [15] Concerns also emerged about the effect of the coincidence of rush hours with the hottest hours of the day on air pollution. [13] [16] Furthermore, an increase in the number of assaults on children in the morning was observed, and insurance companies reported a rise in the number of accidents. [12] [17] Due to all of these concerns and complaints, it became clear that situation could not continue much longer without a new analysis. In December 1995, the government (now led by António Guterres) commissioned a report to Lisbon Observatory on the issue of Portuguese standard time. [18] In February 1996, the Observatory report was released and it concluded that owing to the geographical position of Portugal, the country should re-adopt Western European Time as its standard time zone, a position that the policymakers accepted. [16] [19]
In 1996, new legislation was approved. By Decree-Law 17/96, mainland Portugal returned to the Western European Time time zone. [3] [16] DST would continue to be observed as WEST (UTC+01:00) from the last Sunday in March to the last Sunday in October, thus also adopting the then recently changed EU rules regarding DST. [2] [3] [16] In the same year, Azores and Madeira regional parliaments also approved regional laws that adapted the new EU rules to their time zones, thus ensuring that DST would be observed from the last Sunday in March to last Sunday in October in the entire Portuguese realm. [20] [21] [22]
In 1996 Portugal adopted ISO 8601 via EN 28601 as NP EN 28601:1996. [23]
The Astronomical Observatory of Lisbon publishes the official time via the Network Time Protocol (NTP), e.g. via "ntp02.oal.ul.pt" and "ntp04.oal.ul.pt". [24]
The IANA time zone database contains three zones for Portugal. Columns marked with * are from the file zone.tab from the database. [25]
| c.c.* | coordinates* | TZ* | comments* | UTC offset | DST | Notes |
|---|---|---|---|---|---|---|
| PT | +3843−00908 | Europe/Lisbon | Portugal (mainland) | +00:00 | +01:00 | |
| PT | +3238−01654 | Atlantic/Madeira | Madeira Islands | +00:00 | +01:00 | |
| PT | +3744−02540 | Atlantic/Azores | Azores | −01:00 | +00:00 |
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, counted from midnight. At different times in the past, it has been calculated in different ways, including being calculated from noon; as a consequence, it cannot be used to specify a particular time unless a context is given. The term 'GMT' is also used as one of the names for the time zone UTC+00:00 and, in UK law, is the basis for civil time in the United Kingdom.
A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.
Western European Summer Time is a summer daylight saving time scheme, 1 hour ahead of Greenwich Mean Time and Coordinated Universal Time. It is used in:
Western European Time is a time zone covering parts of western Europe and consists of countries using UTC±00:00. It is one of the three standard time zones in the European Union along with Central European Time and Eastern European Time.
Summer time in Europe is the variation of standard clock time that is applied in most European countries in the period between spring and autumn, during which clocks are advanced by one hour from the time observed in the rest of the year, with a view to making the most efficient use of seasonal daylight. It corresponds to the notion and practice of daylight saving time (DST) to be found in many other parts of the world.
Time in New Zealand is divided by law into two standard time zones. The main islands use New Zealand Standard Time (NZST), 12 hours in advance of Coordinated Universal Time (UTC) / military M (Mike), while the outlying Chatham Islands use Chatham Standard Time (CHAST), 12 hours 45 minutes in advance of UTC / military M^ (Mike-Three).
Moscow Time is the time zone for the city of Moscow, Russia, and most of western Russia, including Saint Petersburg. It is the second-westernmost of the eleven time zones of Russia. It has been set to UTC+03:00 without DST since 26 October 2014; before that date it had been set to UTC+04:00 year-round on 27 March 2011.
Australia uses three main time zones: Australian Western Standard Time, Australian Central Standard Time, and Australian Eastern Standard Time. Time is regulated by the individual state governments, some of which observe daylight saving time (DST). Australia's external territories observe different time zones.
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Time in Brazil is calculated using standard time, and the country is divided into four standard time zones: UTC−02:00, UTC−03:00, UTC−04:00 and UTC−05:00.
Time in Chile is divided into three time zones. Most of Continental Chile uses the time offset UTC−04:00 in winter time and UTC−03:00 in summer time, while the Magallanes and Chilean Antarctica region uses the time offset UTC-03:00 the whole year. Additionally, Easter Island uses the time offset UTC−06:00 in winter time and UTC−05:00 in summer time.
UTC±00:00 is an identifier for a time offset from UTC of +00:00. In ISO 8601, an example of the associated time would be written as 2019-02-07T23:28:34+00:00. It is also known by the following geographical or historical names:
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Europe spans seven primary time zones, excluding summer time offsets. Most European countries use summer time and harmonise their summer time adjustments; see Summer time in Europe for details.
Metropolitan France uses Central European Time as its standard time, and observes Central European Summer Time from the last Sunday in March to the last Sunday in October. With its overseas territories, France uses 12 different time zones, more than any other country in the world.
Daylight saving time in the Americas is the arrangement in the Americas by which clocks are advanced by one hour in spring and moved back in autumn, to make the most of seasonal daylight. The practice is widespread in North America, with most of Canada, Mexico, and the United States participating, but much less so in South America.
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As of 2022, daylight saving time is used in the following Asian countries:
Daylight saving time (DST), also known as summer time, is the practice of advancing clocks during part of the year, typically by one hour around spring and summer, so that daylight ends at a later time of the day. As of 2022, DST is observed in most of Europe, most of North America and parts of Asia around the Northern Hemisphere summer, and in parts of South America and Oceania around the Southern Hemisphere summer. It was also formerly observed in other areas.
Spain has two time zones and observes daylight saving time. Spain mainly uses Central European Time (GMT+01:00) and Central European Summer Time (GMT+02:00) in Peninsular Spain, the Balearic Islands, Ceuta, Melilla and plazas de soberanía. In the Canary Islands, the time zone is Western European Time (GMT±00:00) and Western European Summer Time (GMT+01:00). Daylight saving time is observed from the last Sunday in March to the last Sunday in October throughout Spain.
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