There are six types of elections in the United Kingdom: United Kingdom general elections, elections to devolved parliaments and assemblies, elections to the European Parliament, local elections, mayoral elections and Police and Crime Commissioner elections. Elections are held on Election Day, which is conventionally a Thursday. Since the passing of the Fixed-term Parliaments Act 2011 for general elections, all six types of elections are held after fixed periods, though early elections to parliament and the devolved assemblies and parliaments can occur in certain situations. Currently, six electoral systems are used: the single member plurality system (first past the post), the multi member plurality system, party-list proportional representation, the single transferable vote, the additional member system and the supplementary vote.