Until 1940 the country shared the same time zone as Portugal. Franco decided that Spain should flow with Nazi Germany and instead of Greenwich Mean Time, which is the one that corresponds to it geographically as well as Portugal or the Canary Islands, it should be modified.

This dictator also decided to bring to Spain the Bourbons, of French origin, who, while waiting for the next popular referendum, will decide whether Spain will be republican again or not, as in the municipal elections of April 1931, taken as a plebiscite between monarchy or republic and that made Alfonso XIII leave Spain.

The geographical location of Galicia, whose time zone is more aligned with Madeira or the Canary Islands, Portugal can be changed as Spain or maybe as Portugal independently because here it gets dark later than in other areas of Spain.

The calendar of winter and summer time changes according to Article 5 of Royal Decree 236/2002 must be updated every five years in the BOE which corresponds to the next year 2026.