Also, the Diomede islands are not the only ones in close proximity but on opposite sides of the International Date Line. Samoa (UTC+13) and American Samoa (UTC-11) are even more extreme, being 24 hours apart, i.e. in the "same" time zone but on different days.
https://en.wikipedia.org/wiki/And_the_Sea_Will_Tell
It makes an interesting read.
Also, the Diomede islands are not the only ones in close proximity but on opposite sides of the International Date Line. Samoa (UTC+13) and American Samoa (UTC-11) are even more extreme, being 24 hours apart, i.e. in the "same" time zone but on different days.