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Comment by sschueller | Hacker News Reader

Why can't we do a 30 minute shift? Then we get rid of this back and forth and we get the best of both worlds. What am I missing here?

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It depends on what you are optimizing for and where you are optimizing for. Standard and Daylight times have different meanings in different sides of the time zone. On Eastern edges of a time zone Standard time truly is more "standard" with respect to solar noon. On Western edges of a time zone Daylight time starts to be more preferable and closer to solar noon. Half-hour between the two might favor the "middle" of the time zone perhaps and/or it might just leave all the populations on either side of the time zone unhappy.

Arguably our timezones have grown too wide to accommodate preferences of both edges. Our timezones were optimized for train schedules and full hour-wide zones made some sense based on the speed of train travel. Maybe instead of trying to pick just "Standard" Time or just Daylight Time we should instead be talking about narrowing our time zones (to half-hour wide, perhaps) and better figure out what geography we are best trying to represent versus solar noon, the center of a timezone, one edge or the other.

It's an interesting idea. 'Micro time zones' of sorts. People already survive on time zone boundaries. Why stop at 30 minutes?

It'd be most convenient for local events, but maybe not for non-local events.

I'd open my bar at the most eastern point.

This is the case as it is in Australia, they have five timezones. https://www.timeanddate.com/time/australia/time-zones-backgr...

I don't know exactly how that fares with scheduling and whatnot but it's been implemented.

Historically time zones were the purview of cities. (Often it was the banks and/or churches in a city coordinating time for that city and its relation to solar noon.) It's why the IANA preferred timezone identifiers are cities like America/New_York, America/Mexico_City, Europe/Berlin, etc. Go back far enough in the IANA timezone database (which is used for all sorts of things on the internet and in general computing today) and you'll find all sorts of interesting historic timezone offsets for cities. Some not even to a round offset like 30 minutes, but to single minute or even fractional minute (seconds, milliseconds) offsets from UTC.

I don't know if a return to per-city offsets is the best idea. Software could handle a lot of the messy details for us in ways that the railroads could not have taken advantage of with only so much space for physical clocks. But a return to per-city offsets isn't really the worst idea either if we are looking at what problems Daylight Saving Time was supposed to solve and didn't solve very well.

As someone who has to schedule meetings with people in India, the half hour offset is really confusing and hard to get used to. Half the year is is 11.5 hours and the other 12.5 hours. I never remember which is which.

The change isn't because of India, it's because you change your clocks.

The half hour is only confusing if you're not used to it.

(Nepal has a 45 minute offset, which is a great timezone to check things work. Chatham Island in NZ too)

10 minute adjustment on the first of each month.

daily adjustments.

One negative would be you'd need to get the entire world on board. I mean, there are a handful of off-by-30 time zones in existence, but the rest of the world is in sync in that way.

India and Sri Lanka use a 30 minute offset (+5:30 all year round). So does part of Australia (Northern Territory is +9:30 year round, South Australia is +9:30 standard time and +10:30 daylight saving.) And one Canadian province (the most populated parts of Newfoundland and Labrador are on -3:30 standard time, -2:3 daylight saving.) It doesn't cause any of these places any major difficulty. If the US were to adopt 30 minute timezone offsets, I don't see how that would cause the US any major difficulty either. Probably would break some buggy software which was written for US domestic use only and assumes timezone offsets are hourly, but buggy software can be patched or replaced.

Just don't assume half hour offsets either ;)

Example: New Zealand, Chatham Islands: UTC +12:45 / +13:45

https://www.timeanddate.com/time/time-zones-interesting.html

Also Nepal is UTC+5:45, and there is a sparsely populated region of Australia – around the settlement of Eucla, on the border between the states of Western Australia and South Australia – which unofficially observes UTC+8:45, although that is not its legal time zone.

Historically even weirder offsets have been used:

UTC-00:44 – Liberia, 1919–1972

UTC+04:51 – Bombay (now Mumbai), India, prior to 1955

UTC+05:40 – Nepal, 1921–1986

UTC+07:20 – daylight saving time in Malaya (now Malaysia's peninsular region) and Singapore, 1933–1941

But at least all of those were to the minute. In the past, some places have even used offsets to the second:

UTC-00:43:08 – Liberia, prior to 1919

UTC-00:25:21 – Ireland, 1880–1916

UTC+05:41:16 – Nepal, prior to 1920

Most software probably handles minute-based offsets correctly, even weird ones which aren't on the hour/half-hour/quarter-hour mark, but very little software would support seconds-based offsets. Prior to the introduction of standardised time zones, people used mean local solar time – which can be defined to as precise an accuracy as you'd like, down to the second, even the sub-second, provided you have a sufficiently accurate measurement of your location – and some early attempts at time zones just used the capital's local mean solar time down to the nearest second, hence the seconds-based offsets. Most clocks were not very accurate in those days, rendering the seconds-based offset largely theoretical. I doubt anybody is going to do that again.

The most crazy is of course the Netherlands between 1909 and 1937, with an offset of 19 minutes and 32.13 seconds (the tzdb excludes the .13 seconds as that's not supported). Not sure if there's been other timezones with subsecond definitions.

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