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
1884 prime meridian system
International Meridian Conference
Time in Portugal