A user of my crossword puzzle pointers page wrote to say he was seeing wrong dates on the page. I wasn't, so I asked him what browser and operating system he was using, and what time zone he was in. The time zone was the interesting bit: Venezuelan time is four and a half hours behind UTC, which made me think that either Javascript or I had a problem with partial-hour offsets. I was wrong.
The real problem is that Javascript thinks Venezuela is 19:30 east of UTC instead of 4:30 west. I can work around that, I thought, by subtracting a day from the time in any time zone that's impossibly far east. But how far is that?
Twelve hours is the obvious answer, so naturally it's wrong. According to Wikipedia's List of time zones, the easternmost zone is UTC+1400, used by the Line Islands. These islands are mostly possessions of Kiribati, which is centered much further west. The Line Islands' unusual time zone has the advantage of making it usually the same day as in Tarawa, the capital city and island.
Amusingly, the Line Islands used to observe the same time as Hawaii and the Aleutian Islands (UTC-1000), but switched to their current zone by skipping the entire day of 31 December, 1994.
I did not know.
