Time in Europe:

light blue	Western European Time / Greenwich Mean Time (UTC)
blue	Western European Time / Greenwich Mean Time (UTC)
	Western European Summer Time / British Summer Time / Irish Standard Time (UTC+1)
red	Central European Time (UTC+1)
	Central European Summer Time (UTC+2)
yellow	Eastern European Time / Kaliningrad Time (UTC+2)
golden	Eastern European Time (UTC+2)
	Eastern European Summer Time (UTC+3)
light green	Further-eastern European Time / Moscow Time / Turkey Time (UTC+3)

Light colours indicate where standard time is observed all year; dark colours indicate where a summer time is observed.

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.^[1]

History[edit]

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), for mainland Portugal it was 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, in Portuguese) was observed for the first time in 1916, during World War I, and it consisted in advancing clocks by 1 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 DST’s start and end dates which were often changed.^[3]

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”.^[3] Situation returned to normality after 1945, with the end of World War II, and normal 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 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).^[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 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.^[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. So, in 1976, Portugal adopted WET (UTC+00:00) as its standard time.^[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, instead of GMT.^[2][10]

In 1992, during 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).^[3][11] 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.^[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 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.^[12][13] Obviously, 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 fall asleep on the early morning classes.^[12][15] 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.^[12][15][14] 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.^[13][15] Concerns also emerged concerns 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 WET (UTC+00:00) as its standard time zone, a position that the policymakers decided to follow.^[16][19]

In 1996, new legislation was approved. By Decree-Law 17/96, mainland Portugal returned to the WET (UTC+00:00) 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 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.^[20][21][22]

Date and time notation[edit]

In 1996 Portugal adopted ISO 8601 via EN 28601 as NP EN 28601:1996.^[23]

Time signalling[edit]

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]

IANA time zone database[edit]

The IANA time zone database contains 3 zones for Portugal. Columns marked with * are from the file zone.tab from the database.

References[edit]

Further reading[edit]

• 
  Fernando Correia de Oliveira (2003). História do tempo em Portugal: elementos para uma história do tempo, da relojoaria e das mentalidades em Portugal (in Portuguese). SOCTIP. p. 324. ISBN 978-972-98861-1-9.