These tests add coverage for a corner case in the TZDB. In spring 1919,
the America/Toronto time zone switched to DST at 23:30 on March 30th,
skipping an hour ahead to 00:30 on March 31st. This meant that both March
30th and March 31st were 23.5-hour days.
See: https://github.com/tc39/proposal-temporal/issues/2910