In appreciation of Greenwich Mean Time

In My Humble Opinion
1

Greenwich, England, is a bit East down the River Thames from London proper. Wisely averting a world conflict over meridians, an astronomer chose Greenwich to be the zero-hour meridian, and thus 24 of them around the ellipsoid world.

It was picked up by the railways as “railway time,” and then sailors started using it to know where they were, east-west based, as they carried really accurate clocks, and knowing where you are on the seas is even better than trying to make the trains run on time.

It was later upgraded to UTC (Universal Coordinated Time) as GMT wanders around a bit, and Astronomers also need accurate time. And because the Earth has an atmosphere, the friction of air slows it down ever so much, and occasionally there is a “leap second.” The very consistent decay of Caesium atoms controls the exact, to many decimal places, time.

Trivia question? What country lives all year under Greenwich Mean Time?

Iceland!

It all worked so well, yet, apparently, to save energy during wartime, something called “Daylight Saving Time” became a thing. And after the wars, people got used to staying with it.

Just as it was becoming nearly effortless with computers and smartphones, to change the time (outside the kitchen), some wise countries said, “Let’s stop doing this stupid thing. Let’s vote to stay with one of the other and never ever try to save daylight again.” So Russia voted by province, and Moscow would remain 3 hours ahead of GMT. Due to reasons, they changed to GMT+4, but are all now back to where the provinces voted to be.

I know sometime around Brexit / Scottish Independence / Boris Johnson / Covid-19, there had been a plan for all EU countries to vote with 0 / +1 and stick with it till they didn’t want to.

For reasons that has not occurred. So most of the world will, on the last midnight on the last Sunday (March 29th) this year. GMT isn’t going to change, and UTC changing would cause chaos.

So am I the Grinch to propose we do what we proposed to do (in Europe)? The USA can and will do what it wants. I suggest they follow China and have a singular American time.

It won’t affect the world fund trading at all. Forex, shmorex.

Zulu-time forever!

2

Having worked a lifetime in a Zulu-centric industry, I sure agree it’d be nice to just use that always and everywhere.

Of course humans being humans, such a change is impossible. Had we settled on that 150 years ago, it’d be utterly ordinary and everyone would be on board. Now? Fuggeddaboudit!

3

Yeah, even when referendums on choosing to stay in real or, as they call it here, “Summer Time” are done (Russia), they sometimes change it back or forget they were going to do it.

I’m not saying the whole world should adopt GMT, just that this nonsense of changing twice a year should cease. Pick regular or summer. And doesn’t have to be as wide as 5 former time zones of China, now all being on China time.

At least, here in the UK. I went out for what I thought was a late run at 5:30 thinking I’d need my hi-vis jacket - yet it was only late in the daytime. I don’t need 10PM sunsets in June.

4

We do this thread every year. Twice a year actually.

How DST or regular time and changing or not changing lines up w folks’ lives depends very greatly on how far north / south they live and also how far east / west within their time zone. And whether their zone is stretched, shrunk, or shifted east/west for essentially political or historical reasons to which the sun’s timing pays no heed.

If we were serious about making time changes fit everyone better, they’d be broken out by latitude as well as longitude and we’d move the far polar folks maybe 90 minutes in three 30-minute increments, while moving the more tropical folks not at all. With folks in the temperate mid-latitudes moving 60 minutes.

The alternative is leaving the clocks alone and mandating school and business opening and closing times to change around the year. Or depopulate the parts of the planet where winter daylight is insufficient for school and work to fit in the hours of daylight.

5

I traveled to Australia a few times on business around twenty years ago. I was there over one of the time changes and it was a week off of the US one so the time relative to the US was either (as I recall) three, four or five hours different (technically 20, 21 or 22 hours different if my math is right).

6

Now we’re talking. Who wants to chip in some money to pool our resources and buy a few atomic bombs?

7

The British Columbia government recently announced the province will move to daylight saving time as usual this weekend and will remain on Pacific Daylight Time permanently. I’d prefer it stayed on PST, but nobody asked me.

In 1988, the province of Newfoundland (emphasis on the last syllable, please) moved to Double Daylight Saving Time, moving ahead 2 hours. This was apparently done at the forceful request of a cabinet minister who wanted to play more softball in daylight hours. It was, ah, cumbersome.

Mind you, this is the same province where a poacher on a snowmobile eluded the RCMP, the Royal Newfoundland Constabulary, and conservation officers for hours. When he was finally apprehended, it was discovered the culprit was the provincial minister of the environment.

8

Nonsense; no need for weaponry. Just tell them they’ll never have to trudge through snow again and most of them will move eagerly.

9

Good point.

I suppose I can’t be prosecuted for doing it your way, either.

10

Iceland does just fine spending a couple of months with no sunset, as there will be a couple of months with no sunrise. And they don’t really need heat either, with the underground heated steam pools. Perhaps parts of Finland, too. And Bath, England, was popular with cold Romans who never cared what time it was.

St. Petersburg embraces its “White Nights”, even if there are no tourists now. Whoo hoo! You can see the drawbridges raised and lit, as oil tankers cruise under them. Sunset: 10 PM, Sunrise 2 AM. Reverse that for the middle of winter (rise 10 AM, set 2 PM).

I’m in the low 50°’s and am planning a move into the high 40°’s latitude this summer, so it’ll matter even less.

There was supposed to be a European referendum, and even after Brexit, the UK was invited. Didn’t happen. I’ll only have my car clock to change, and I’ll totally enjoy going out for a sunny run at 2130 British Summer Time.

11

Just to be pedantic, one of all of our favorite pastimes, UTC, GMT, and Zulu are not the same thing (even though they sort of are).

  • UTC is the a time standard from which the various time zones are derived.
  • GMT is the time zone which is at UTC+00:00, and contains some European and African countries.
  • Zulu is the military time zone which is at UTC+00:00

The main place this becomes important is when describing time in countries that spend only part of the year in GMT. Soon the UK will enter BST (British Summer Time), which is UTC+01:00.

The main place of confusion is if someone gives a time of 12 June, 10:30 GMT. Does that really mean 10:30 UTC or 10:30 BST? Same difference as inappropriately using EST or EDT as a label.

For an international event I’m hosting I’ve had to put together a long table like this, and make sure I get all my time zone abbreviations right. I include “Corresponding UTC” for the purposes of exactness.

City Start End Time zone
Boston, USA 09:00 18:00 EDT
São Paulo, Brazil 10:00 19:00 BRT
Corresponding UTC 13:00 22:00 UTC
London, United Kingdom 14:00 23:00 BST
Amsterdam, Netherlands 15:00 00:00 +1 day CEST
12

ISO 8601 is the standard used in software. I personally do not like ZULU becase date-time convertions are a pain in the ass, and we have 8601 to guide us through the really stupid way we humans have implemted date and time.

But I accept ZULU as second best. And technically… ZULU is coded in ISO 8601 format.

Sorry. I am a date nerd and a code nerd. Coincidentally, my birthday this year is 2026-03-07T12:00:00Z (UTC)

13

The one thing I hate about 8601 is that stupid “T” that separates the date from the time. It should be a punctuation mark. Colon would be fine. Hyphen or slash would be fine. But that T is ugly as hell.

I was always surprised how many seemingly competent programmers didn’t see a problem using local time everywhere. Even though local time is ambiguous for an hour each year, discontinuous twice a year, and different for different users. I had to have the “please use local time only for display” conversation so many times in my career.

14

In many countries, including mine (South Africa) we do not have daylight saving time. But I have worked with clients in the UK and the US whose times do change. ISO 8601 is not just a date format, it is possibly the closest thing, for me, to a religion.

I am weirdly obsessive about the “one true standard”

15

Now we have a need for weaponry as I like trudging thru snow. :angry:

I trudged thru over snow last week, thru today, & will trudge over or thru snow (depending upon conditions, but I do expect over) again next weekend, which will probably be my last time for this winter.

16

You certainly are.

8601 is a human readable display format and string-based interchange format. Nothing more. As such it’s about 2% of what a complete date / time storage, computation, transmission, and display system needs to include.

For string-based interchange (e.g. JSON, XML, etc.), there’s no good excuse for using anything other than 8601. You’re certainly correct to evangelize for that use case. But … For all other purposes in that chain of custody, it’s either a bad choice, or not even relevant.

Even as to display formats, it’s a terrible choice for a non-technical audience. Which is the 99.999% use case for date / time display. The correct choice for non-technical users is always the user’s culturally expected format. No matter how illogical and inconsistent that may be.

17

The major advantage (IMHO) is that the base format might seem a bit weird to non-programmers, but there are numerous libraries in many languages to convert it into a format that might be more familiar to users.

Like the US… I don’t know why, for example, the infamous September 11 attack is “9/11”.

To me, in a different culture, that is December the ninth, time to do last minute Xmas shopping.

Whereas 2001-09-11T08:46 - the impact of the plane on the South Tower is extremely clear to me.

Depending on the programing language somewhat, the ISO 8601 can be converted to any preferred format. As long as it is ISO 8601 in the database, I don’t care too much about the displayed date which the user gets to see.

(8601 is also easily sortable, something that us nerds really value.
Which comes first, 27 January or 5 April? That is a solved problem.
).

18

If it’s ISO 8601 in the database, you have a very F-ed up database. In the database it should be some internal datatype, not a Unicode (or worse yet ASCII) string, regardless of the format of the contents of that Unicode/ASCII string.

Here’s an example of database datatypes.

Yes, if you need to serialize those datatypes into a text string for transmission across a text-only protocol, you should serialize to 8601 and nothing else. And the same going the other direction if you need to use a text-only protocol somewhere along the path towards database storage.

But in your database they should be dedicated date/time-related datatypes and in your programming language they should be dedicated date/time object types. And for display you should be using culturally appropriate date / time formats. All else is grievous error.

Lots and lots of apps can do lots and lots of work with dates / times with no involvement with 8601 whatsoever. And rightly so.

19

Because in the US we always write the Month first. That’s just how it is. It’s not complicated and is not a big deal.

Now if you call December the 11th month, that is weird. What culture does that?

20

Not sure how it did that (or that it did). Greenwich was the UKs favored meridian for navigation, but other nations persisted in using their own for some time after.

And so I think you have to have that backwards. GMT was the basis for determining longitude on UK vessels at sea from the adoption of accurate seagoing chronometers and some years before railroads were much of a thing at all. UK railroads then started using it as well some decades later. Then, some decades after that an international convention formally endorsed the use of GMT at sea as an international standard.