Time Zones

Yesterday my grandma and I had a conversation about time zones, which started when it came up that China spans several time zones but only uses one (UTC+8). We started talking about how that was unusual, and I put forth the idea that things would be less confusing without time zones, i.e. if everyone used UTC.

With the current system, 8:00 in California is three hours after 8:00 in New York. You can be talking to someone, live, who is “already in tomorrow”. How does this make sense?

On the flip side, 8:00 local time tells you something about the position of the sun: it’s morning. A school day goes from around 8:00AM to 3:00PM everywhere. So there’s some reason for it.

The question is, what is clock time supposed to tell us? If it’s the position of the sun, then I guess we’re good. But since we live in an increasingly connected world (across time zones), and have artificial lighting (so as not to be constrained by the sun), it might be more important to say “when events happened”.

If everyone used UTC regardless of where they lived, then when something happened in China at 8:00Z, and it’s 11:00Z now, it happened three hours ago. The date is the same for everyone around the world; with no time zones, there’s no International Date Line or confusion that goes with it. It’s a lot easier to tell how long plane rides are, and you never need to reset your watch.

You would still need to reset your daily schedule, though. On the West Coast (UTC-8), school would happen from 16:00Z (4:00PM UTC) to 21:00Z. In Korea (UTC+9), school happens from 23:00Z to 18:00Z the next day. This is probably too weird for real use.

Still, for engineers and programmers, times are always stored in UTC, or at the very least with a time zone attached. You have to do this; websites and software are global, and the same person might use the same programs in multiple time zones continuously, by crossing lines on a train, or by being logged in through two different devices. Without a reference point, you can’t really say when something happens.

Interestingly, we treat our calendars the opposite way: January is winter in the northern hemisphere, but summer in the southern. (My friend from South Africa says they still put out big fake snowflakes and stuff for Christmas…which I guess is no weirder than doing it in California where it just rains.) This is a case where we do have one system for everyone, instead of flipping the names of the months in the southern hemisphere…probably because it doesn’t make sense to gradually slide months forwards based on latitude. (“Summer” and “winter” don’t really have the same meanings at the equator.)

In any case, the one thing we agreed on was that switching was harder than either system on its own. The world will be sticking with time zones (with UTC timestamps) for a while longer.

P.S. As weird as time zones may be, Daylight Savings Time is even worse; at least you can refer to different time zones by saying “UTC-8” or whatever. On the day when DST ends, you officially set the clocks back an hour at 2:00AM. That means that the time will be 12:00, 12:30, 1:00, 1:30, 1:00, 1:30, 2:00, 2:30…with two “1-2” hours in the same “day”. (All that really happens is a change from UTC-7 to UTC-8.)

Other than giving the time zone (1:00-0700 vs. 1:00-0800), there is no standard way to refer to which 1:00 you mean.

P.P.S. Who decided the day starts at 12:00 and not 1:00? If you’re going to use zero-based indexing, the least you could do is start at zero.