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Comment by AnimalMuppet | Hacker News Reader

A lot of us expect that "noon" has some connection to "sun at its highest point in the sky". Having that happen at 10 PM just feels wrong.

But in fact, the military does have one standard time - Zulu time.

Why have so many time zones? Well, they were originally introduced by railroads in the 1880s. Back then, "noon" was defined as "highest sun", so deviating very far from that was unreasonable. But also, railroads didn't run very fast back then. Each time zone was something like 700 miles across. That was enough to give enormous operational improvements. Removing the transitions (going to all one time zone) would have added only a little additional improvement.

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"the military does have one standard time - Zulu time"

Nah they don't. Skipping over the (common on the internet) parochiality of assuming that US military practice is just 'what the military does'...

The US military certainly uses UTC/Zulu time for time stamping messages and coordinating operations globally, and timekeeping during extended missions (like submarine patrols, or air missions), but military bases and even surface vessels underway keep somewhat local time. They don't use Zulu time - that would mean the date changes in the middle of the day. You wouldn't be able to use words like 'next Tuesday' without having to disambiguate. It'd be crazy.

Zulu - Z - is just the last of the alphabetically named military timezones: https://en.m.wikipedia.org/wiki/Military_time_zone, which is a NATO standard.

Zulu is used for aircraft scheduling, because it makes it simpler.

Outside of that, the military recognizes two times, zero dark hundred and late as hell.

I think you hit on the right answer.

The justifications given above don't really make sense - "how would you know when to call Sydney" or "the sun being overhead at 10PM would feel strange". They are just rationalizations of a system that we're used to.

But everywhere around the world, people want the date to change at a time when most things are closed and most people are asleep - which coincides with night-time for obvious reasons. This is effectively more important than having the date change at the same time for all of us.

I'm still not sure the costs outweigh the benefits, but I agree that this is the only concrete requirement that can't be solved with time, slow cultural change, and adjustments to some software.

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