国际日期变更线
Alaska was on the western side of the International Date Line, since Russian settlers reached Alaska from Siberia. In addition, the Russian Empire was still using the Julian calendar, which had fallen 12 days behind the Gregorian calendar. In 1867, the United States purchased Russian America and moved the territory to the east side of the International Date Line. The transfer ceremony took place at 3:30p.m. in the capital of New Archangel (Sitka), on Saturday, (Julian), which was Saturday, (Gregorian) in Europe. Since Alaska moved to the eastern side of the International Date Line, the date also moved back to Friday, , now known as Alaska Day.