

The fastest time to visit all sovereign countries (overall) is 1 year and 189 days and was achieved by Taylor Demonbreun (USA) between 1 June 2017 and 7 December 2018.
Taylor visited the 195 countries requested by the guidelines - the 193 UN Member States as of December 2018, the Vatican, a non-member observer State, and Chinese Taipei, which does not have member status but is effectively sovereign.