|Western European Time / Greenwich Mean Time (UTC)|
|Western European Time / Greenwich Mean Time (UTC)|
|Western European Summer Time / British Summer Time / Irish Standard Time (UTC+1)|
|Central European Time (UTC+1)|
|Central European Summer Time (UTC+2)|
|Eastern European Time / Kaliningrad Time (UTC+2)|
|Eastern European Time (UTC+2)|
|Eastern European Summer Time (UTC+3)|
|Further-eastern European Time / Moscow Time / Turkey Time (UTC+3)|
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, so that every year, continental Portugal and Madeira temporarily use UTC+01:00, and the Azores temporarily use UTC+00:00.
In the early 19th century, Portugal adopted mean solar time.Navy (located in Lisbon) and Coimbra Astronomical Observatories calculated solar time to be used as legal time in their longitude regions. 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. 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.
In 1911, it was agreed that standard time in Portugal should be defined in accordance with the 1884 prime meridian system.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), for mainland Portugal it was adopted UTC+00:00 as its time zone. 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. These time zones were adopted on 1 January 1912.
Daylight saving time (Hora de Verão, in Portuguese) was observed for the first time in 1916, during World War I, and it consisted in advancing clocks by 1 hour.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.
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 DST’s start and end dates which were often changed.
In the years 1942–1945, during World War II, Portugal, not only advanced clocks by 1 hour during DST, as also advanced them by another 1 hour during some months of those years, coming to have clocks 2 hours ahead of GMT, during that “double DST”.Situation returned to normality after 1945, with the end of World War II, and normal DST continued to be observed. In 1948, it was approved that DST should be observed from the first Sunday in April to the first Sunday in October.
From 1966 on, DST started to be observed year-round, so that, in practice, Portugal changed its time zone from WET (UTC+00:00) to CET (UTC+01:00).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 9:00, 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. Furthermore, in the 1970s, the idea of reintroducing DST as an energy saving measure gained strength in Europe as well as in Portugal. 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. So, in 1976, Portugal adopted WET (UTC+00:00) as its standard time. DST started to be observed every year as WEST (UTC+01:00) usually from early April to later September. From 1981 on, DST started to be observed from the last Sunday in March to the last Sunday in September.
In 1986, time in Portugal began to be calculated in accordance with UTC, instead of GMT.
In 1992, during Aníbal Cavaco Silva government, by Decree-Law 124/92, mainland Portugal officially changed its time zone from WET (UTC+00:00) to CET (UTC+01:00).Differently from the 1966 move to CET, this time DST was to be observed, as CEST (UTC+02:00), from the last Sunday in March to the last Sunday in September. 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. However, the measure quickly proved to be a failure in achieving its objectives and become unpopular: as in the 1966–1976 period, on winter mornings, the sun was still rising at 9:00, and people went to work in the dark. Obviously, children also began the school day in darkness, with repercussions on their standards of learning, school performance and sleeping habits. It was even common that children fall asleep on the early morning classes. On summer evenings, the usage of CEST was revealed to have a disturbing effect on people’s sleeping habits, particularly children's ones, as the sun was still setting at 22:00 or 22:30, so the sky was only completely dark towards midnight. A company hired by European Commission conducted a study which concluded that, in fact, there were no energy savings because in the early morning, due to the dark, workers turned on lights in their offices, and they forgot to turn them off, leaving them switched on for the rest of the morning, which increased energy consumption. Concerns also emerged about the effect of the coincidence of rush hours with the hottest hours of the day on air pollution. 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. 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. In February 1996, the Observatory report was released and it concluded that owing to the geographical position of Portugal, the country should re-adopt WET (UTC+00:00) as its standard time zone, a position that the policymakers decided to follow.
In 1996, new legislation was approved. By Decree-Law 17/96, mainland Portugal returned to the WET (UTC+00:00) time zone.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. In the same year, Azores and Madeira regional parliaments also approved regional laws who adopted the new EU rules to their time zones, thus making that DST started to be observed from the last Sunday in March to last Sunday in October in the whole country.
In 1996 Portugal adopted ISO 8601 via EN 28601 as NP EN 28601:1996.
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".
The IANA time zone database contains 3 zones for Portugal. Columns marked with * are from the file zone.tab from the database.
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, reckoned 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 precise time unless a context is given.
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.
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.
Hong Kong Time is the time in Hong Kong, observed at UTC+08:00 all year round. The Hong Kong Observatory is the official timekeeper of the Hong Kong Time.
The time in China follows a single standard time offset of UTC+08:00, despite China spanning five geographical time zones. The official national standard time is called Beijing Time domestically and China Standard Time (CST) internationally. Daylight saving time has not been observed since 1991.
There are eleven time zones in Russia, which currently observe times ranging from UTC+02:00 to UTC+12:00. Daylight saving time is not used in Russia. From 27 March 2011 to 26 October 2014, permanent DST was used.
Time in Brazil is calculated using standard time, and the country is divided into four standard time zones: GMT−02:00, GMT−03:00, GMT−04:00 and GMT−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
Iran Standard Time (IRST) or Iran Time (IT) is the time zone used in Iran. Iran uses a UTC offset UTC+03:30. IRST is defined by the 52.5 degrees east meridian, the same meridian which defines the Iranian calendar and is the official meridian of Iran.
UTC±00:00 is the following time:
Mexico uses four main time zones since February 2015. Most of the country observes Daylight Saving Time.
Mexico adopted daylight saving time nationwide in 1996, even in its tropical regions, because of its increasing economic ties to the United States. Although the United States changed the schedule for DST beginning in 2007, only the municipalities located less than 20 km from the border have adopted the change. Daylight saving time for Mexico begins the first Sunday of April and ends last Sunday of October; and is usually referred to as the "Summer Schedule".
Brazil observed daylight saving time (DST) in the years of 1931–1933, 1949–1953, 1963–1968 and 1985–2019. Initially it applied to the whole country, but from 1988 it applied only to part of the country, usually the southern regions, where DST is more useful due to a larger seasonal variation in daylight duration.
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 of America participating, but much less so in South America.
As of 2018, daylight saving time (DST) is permanently observed in Morocco. Previously, time was advanced to UTC+01:00 at 02:00 on the last Sunday of March, and reverted to UTC±00:00, defined as Greenwich Mean Time locally, at 03:00 on the last Sunday of October. This practise was continued through October 2018, after which clocks were permanently advanced. An exception was made during the month of Ramadan during which clocks reverted to UTC+00:00.
As of 2017, daylight saving time is used in the following Asian countries:
The only African countries and regions that use daylight saving time are:
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.