Portugal has two time zones and observes daylight saving time

Daylight saving time

Daylight saving time —also summer time in several countries including in British English and European official terminology —is the practice of temporarily advancing clocks during the summertime so that afternoons have more daylight and mornings have less...

. Therefore four different UTC offsets are observed. Continental Portugal

Continental Portugal

Continental Portugal or Mainland Portugal is the designation of the mainland Portuguese territory, located on Europe's Iberian Peninsula....

 and Madeira use UTC+00:00 in winter and UTC+01:00 in summer. The Azores use UTC-01:00 in winter and UTC+00:00 in summer.

History

In 1911 standard time in Portugal was for the first time in relation to the prime meridian established by the 1884 International Meridian Conference

International Meridian Conference

The International Meridian Conference was a conference held in October 1884 in Washington, D.C., in the United States to determine the Prime Meridian of the world. The conference was held at the request of U.S. President Chester A...

, namely as GMT-00:36:44, which was the local mean time at the Astronomical Observatory of Lisbon

Astronomical Observatory of Lisbon

The Astronomical Observatory of Lisbon is located in "Alcântara - Tapada da Ajuda", in the city of Lisbon...

. In 1912 this was changed to GMT. In 1916 it changed to GMT+01:00.

Time signalling

The Astronomical Observatory of Lisbon

Astronomical Observatory of Lisbon

The Astronomical Observatory of Lisbon is located in "Alcântara - Tapada da Ajuda", in the city of Lisbon...

 publishes the official time via the Network Time Protocol

Network Time Protocol

The Network Time Protocol is a protocol and software implementation for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. Originally designed by David L...

 (NTP), e.g. via "ntp02.oal.ul.pt" and "ntp04.oal.ul.pt" .

Tz database

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

c.c.*	coordinates*	TZ*	comments*	UTC offset	DST	Notes
		-
		-
		-

Further reading