[zokier]

> doing it once a century would pretty much guarantee that only the most obsessively robust systems would take it into consideration when being built.

tzdata updates happen all the time (in a relative sense). So code would need to handle those, and I don't see why potential leap hours couldn't be handled like that. Just means that Europe/London eventually will be +01:00 (or is it -01:00, anyways) instead of +00:00 its now.

[fanf2]

Yes, I think that would make sense, but leap hours would be very rare: the first one won’t be needed for 500 years. See the first table at https://www.ucolick.org/~sla/leapsecs/dutc.html

But, leap hours don’t need to be co-ordinated: countries can and do change their clocks to adjust the time of sunrise when they want.

And leap hours will work much longer than leap seconds: leap seconds will become too frequent in 1 or 2 thousand years, but leap hours will just be getting started. See the second table at the same link https://www.ucolick.org/~sla/leapsecs/dutc.html

[Jestar342]

As a former developer of software for an international shipping company: Yup. They happen a lot more frequently than most people realise, I expect. Political reasons (e.g. neighbouring states [as in Sovereign] deciding to unify timezones), coups/wars suspending DST, and so on all usually result in some kind of adjustment, even if it's just the name of the timezone changing.

[wyattpeak]

I can't speak to how different parts of society will interact in hundreds of years, but if today there were going to be a leap hour and programmers requested that we start considering London to be in +01:00, the chances of politicians or public agreeing with that request is nil.

[lifthrasiir]

Sure, we will randomly move the end of the DST from the last Sunday of October to the first Sunday of November and everyone will try to kill us, right? DST is the perfect example that we have a relative freedom in changing time zone offsets.

You are however right that this is a political matter requiring some (but I believe, reasonable) amount of coordination, but timekeeping is in many parts political anyway. Practically speaking countries would implement the change out of necessity and not because of agreements, as one hour deviation is significant enough.

[wyattpeak]

> we have a relative freedom in changing time zone offsets

Who is we in this sentence? Programmers certainly don't, they have to report times and timezones in their software as the populace expects it to be reported. Governments can change timezones, but they're not going to, because the political cost of telling everyone that they're in a new timezone is greater than the political cost of telling programmers where to shove it.

Most of the public will see absolutely no reason why they should have to permanently change the timezone they're in for the sake of a one-time event. And honestly, even as a programmer who'd be doing the fixing, I agree that they're right.

[lifthrasiir]

Governments absolutely can. The updates to tzdata [1] are full of arbitrary changes happening all around the globe, not just for a few weird countries. The example I quoted above is 2007 changes to the United State's DST and a perfect example that governments can push time zone changes with at most marginal perceived benefits. Also remember that the current proposal to abolish leap seconds itself was primarily arosen due to computing complications anyway. Programmers can (indirectly) affect the future of leap seconds than probably any other group else.

[1] https://github.com/eggert/tz/blob/master/NEWS

[gerikson]

Russia decided to just stay on DST with 6 weeks notice a few years ago, thereby instantly creating half a dozen new timezones. And now they're discussing going back to normal time/DST...