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 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 most of
continental Portugal is located west of the 7º 30'W meridian (i.e. in the theoretical zone of
UTC-01:00 time zone), mainland Portugal adopted
UTC+00:00 as its time zone. 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. 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). 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. 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. Therefore, Portugal re-adopted Western European Time (
UTC+00:00) as its standard time in 1976.
Switch to Central European Time 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. 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. 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 fell asleep in the early morning classes. 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 Western European Time as its standard time zone, a position that the policymakers accepted.
Return to Western European Time In 1996, new legislation was approved. By Decree-Law 17/96, mainland Portugal returned to the Western European Time time zone. == Date and time notation ==