Here is more on “Dagen H”, 1967-09-03, when Sweden changed from driving on the left to driving on the right.
Did you know that in 2009 Samoa (previously Western Samoa, as opposed to the nearby U.S. colony), changed from driving on the right to driving on the left? This was the first country to change its driving side in almost three decades, and was motivated to allow Samoans to more easily use inexpensive cars imported from Japan, Australia, and New Zealand, all of which drive on the left.