From ancient Olissipo to modern Western European Time, Lisbon's history reflects centuries of ocean navigation, astronomical precision, and timezone shifts.
c. 2nd century BCE to Present 3 chapters 5 min read
Chapter one
Name & etymology
Earliest documented name
OlissipoAncient Iberian / Graeco-Roman
"Disputed; historically linked to safe harbor or regional hydronyms"
Recorded by Roman and Greek authors such as Pliny the Elder and Strabo, Olissipo is the oldest documented name for Lisbon. While myth attributed its origin to Ulysses and 19th-century etymologies suggested Phoenician Allis Ubbo, pre-Roman written indigenous records do not survive.
c. 2nd century BCE - 27 BCEOlissipo
Disputed; traditionally associated with safe harbor or regional river roots
Used during early Iberian and Roman Republican trade along the Tagus estuary.
27 BCE - 5th century CEFelicitas Julia Olisipo
Happy Julia Olisipo
Official municipal title granted under Emperor Augustus, integrating the settlement into Roman Hispania.
711 - 1147 CEal-Ushbuna
Arabic adaptation of the Roman name Olissipo
Used during Muslim Umayyad and Taifa governance until the Christian Siege of Lisbon.
1147 CE - PresentLisboa
Evolved Portuguese form of Olisipo and al-Ushbuna
Adopted after Afonso I captured the city, becoming the official national capital in 1256.
Chapter two
Timezone history
Current timezoneEurope/Lisbon
Standard
Western European Time (WET / UTC+0)
Daylight
Western European Summer Time (WEST / UTC+1)
1856Adoption of Mean Solar Time1856-01-01
The Royal Observatory of the Navy in Lisbon began broadcasting official mean solar time for public, civic, and naval synchronization across the city.
1911Adoption of Greenwich Mean Time1911-05-26
By government decree on May 26, 1911, continental Portugal adopted Greenwich Mean Time (UTC+0) as its official legal standard, replacing local Lisbon Mean Time.
1916First Daylight Saving Time Trial1916-06-18
Lisbon observed daylight saving time for the first time during World War I, advancing clocks by one hour to WEST (UTC+1).
1992Shift to Central European Time1992-09-27
Portugal shifted continental clocks to Central European Time (UTC+1 standard / UTC+2 summer) to align business hours with European trade partners.
1996Return to Western European Time1996-03-31
After widespread public criticism over dark winter mornings, Lisbon returned to Western European Time (UTC+0 standard / UTC+1 summer).
Chapter three
Timekeeping milestones
Founding of Lisbon Astronomical Observatory
National timekeeping institution
Construction began on the Observatorio Astronomico de Lisboa at Tapada da Ajuda, modeled after Russia's Pulkovo Observatory to serve as Portugal's premier astronomical center.
Inauguration of National Time Service
Official legal time signals
The Lisbon Astronomical Observatory began official operations, assuming legal responsibility for calculating and broadcasting Portugal's standard time.
Port of Lisbon Time-Ball Service
Maritime chronometer synchronization
A telegraphic link connected the Lisbon Observatory to a harbor time-ball, allowing ships navigating the Tagus River to accurately calibrate marine chronometers.