August 3, 2023
+14:00 is the earliest timezone in the world—they are the first to celebrate New Year. -12:00 is the latest—they are the last to celebrate. This means there are 26 time zones in total (not including half time zones).
In other words, there is no time of day during which everyone on Earth is experiencing the same date.
Why is this relevant? For each of my blog posts I need to provide a date. But since dates are tz-aware in JS, people reading in different time zones may see different dates. For some reason, I don’t want that.
In order to have my blog display the same date to as many people as possible, I’ve chosen to suffix each of my dates with T23:59:59+13:00, which means 11:59pm and 59 seconds in TZ +13:00, the second-to-earliest time-zone in the world.
Why +13:00? In my rough approximation, this creates the largest coverage of people who would see the same date as me, covering almost all of Oceania, Asia, Europe, North America and even Hawaii.
The only three time zones that are not covered are -11:00, -12:00, and +14:00, which include:
Kiribati has a population of 121,388 (2021 population estimate), meaning the Line Islands has a population below 12,139. ↩