How to Think About Time in Programming

Time is a mess. Always. The author only scratched the surface on all the issues. Even if we exclude the time dilation of relativity which affects GPS/GNSS satellites - independent of if it is due to difference in gravitational pull or their relative speed over ground, it's still a mess.

Timezones; sure. But what about before timezones got into use? Or even halfway through - which timezone, considering Königsberg used CET when it was part of Germany, but switched to EET after it became Russian. There's even countries that have timezones differenting by 15 minutes.

And dont get me started on daylight savings time. There's been at least one instance where DST was - and was not - in use in Lebanon - at the same time! Good luck booking an appointment...

Not to mention the transition from Julian calendar to Gregorian, which took place over many, many years - different by different countries - as defined by the country borders at that time...

We've even had countries that forgot to insert a leap day in certain years, causing March 1 to occur on different days altogether for a couple of years.

Time is a mess. Is, and aways have been, and always will be.

It is, there are a couple of timezones where not only there is a hour difference, but even a 30 and 45 minutes difference. India is UTC +5:30, and Lord Howe Island is UTC +10:30 / +11:00 and New Zealand, Chatham Islands is UTC +12:45 / +13:45, Iran is UTC +3:30 / +4:30 and so on. Where the format is X / Y, that means X is Standard Time, and Y is Daylight time.

Messy.

I think the full list can be found here: https://www.timeanddate.com/time/time-zones-interesting.html

You can use a Bash script that can give you an exhaustive list based on files from /usr/share/zoneinfo/, i.e. find timezones with non-whole hour offsets.

I don’t understand this. What practical difference does it make making the time to round to the nearest quarter of an hour instead of the nearest hour? Personally, I don’t care if noon (sun is in zenith) happens half an hour before 12:00 or half an hour after.

Why do such time zones exist?

Well, I do not know the answer to that, my guess is that it is for historical, political, geographical, and socio-economic reasons.

For example in terms of India, they had two timezones before they adopted a compromise: UTC+5:30.

Nepal uses UTC+5:45, partly to distinguish itself from Indian Standard Time, reinforcing national identity.

> India, they had two timezones before they adopted a compromise: UTC+5:30.

Truly, a compromise is when nobody is happy. ._\