PSA: North america changes time forward soon, Europe next

1. blog

This is a copy of an email I used to send internally at work and now made public. I'm not sure I'll make a habit of posting it here, especially not twice a year, unless people really like it. Right now, it's mostly here to keep with my current writing spree going.

This is your bi-yearly reminder that time is changing soon!

What's happening?

For people not on tor-internal, you should know that I've been sending semi-regular announcements when daylight saving changes occur. Starting now, I'm making those announcements public so they can be shared with the wider community because, after all, this affects everyone (kind of).

For those of you lucky enough to have no idea what I'm talking about, you should know that some places in the world implement what is called Daylight saving time or DST.

Normally, you shouldn't have to do anything: computers automatically change time following local rules, assuming they are correctly configured, provided recent updates have been applied in the case of a recent change in said rules (because yes, this happens).

Appliances, of course, will likely not change time and will need to adjusted unless they are so-called "smart" (also known as "part of a bot net").

If your clock is flashing "0:00" or "12:00", you have no action to take, congratulations on having the right time once or twice a day.

If you haven't changed those clocks in six months, congratulations, they will be accurate again!

In any case, you should still consider DST because it might affect some of your meeting schedules, particularly if you set up a new meeting schedule in the last 6 months and forgot to consider this change.

If your location does not have DST

Properly scheduled meetings affecting multiple time zones are set in UTC time, which does not change. So if your location does not observer time changes, your (local!) meeting time will not change.

But be aware that some other folks attending your meeting might have the DST bug and their meeting times will change. They might miss entire meetings or arrive late as you frantically ping them over IRC, Matrix, Signal, SMS, Ricochet, Mattermost, SimpleX, Whatsapp, Discord, Slack, Wechat, Snapchat, Telegram, XMPP, Briar, Zulip, RocketChat, DeltaChat, talk(1), write(1), actual telegrams, Meshtastic, Meshcore, Reticulum, APRS, snail mail, and, finally, flying a remote presence drone to their house, asking what's going on.

(Sorry if I forgot your preferred messaging client here, I tried my best.)

Be kind; those poor folks might be more sleep deprived as DST steals one hour of sleep from them on the night that implements the change.

If you do observe DST

If you are affected by the DST bug, your local meeting times will change access the board. Normally, you can trust that your meetings are scheduled to take this change into account and the new time should still be reasonable.

Trust, but verify; make sure the new times are adequate and there are no scheduling conflicts.

Do this now: take a look at your calendar in two week and in April. See if any meeting need to be rescheduled because of an impossible or conflicting time.

When does time change, how and where?

Notice how I mentioned "North America" in the subject? That's a lie. ("The doctor lies", as they say on the BBC.) Other places, including Europe, also changes times, just not all at once (and not all North America).

We'll get into "where" soon, but first let's look at the "how". As you might already know, the trick is:

Spring forward, fall backwards.

This northern-centric (sorry!) proverb says that clocks will move forward by an hour this "spring", after moving backwards last "fall". This is why we lose an hour of work, sorry, sleep. It sucks, to put it bluntly. I want it to stop and will keep writing those advisories until it does.

To see where and when, we, unfortunately, still need to go into politics.

USA and Canada

First, we start with "North America" which, really, is just some parts of USA[1] and Canada[2]. As usual, on the Second Sunday in March (the 8th) at 02:00 local (not UTC!), the clocks will move forward.

This means that properly set clocks will flip from 1:59 to 3:00, coldly depriving us from an hour of sleep that was perniciously granted 6 months ago and making calendar software stupidly hard to write.

Practically, set your wrist watch and alarm clocks[3] back one hour before going to bed and go to bed early.

[1] except Arizona (except the Navajo nation), US territories, and Hawaii

[2] except Yukon, most of Saskatchewan, and parts of British Columbia (northeast), one island in Nunavut (Southampton Island), one town in Ontario (Atikokan) and small parts of Quebec (Le Golfe-du-Saint-Laurent), a list which I keep recopying because I find it just so amazing how chaotic it is. When your clock has its own Wikipedia page, you know something is wrong.

[3] hopefully not managed by a botnet, otherwise kindly ask your bot net operator to apply proper software upgrades in a timely manner

Europe

Next we look at our dear Europe, which will change time on the last Sunday in March (the 29th) at 01:00 UTC (not local!). I think it means that, Amsterdam-time, the clocks will flip from 1:59 to 3:00 AM local on that night.

(Every time I write this, I have doubts. I would welcome independent confirmation from night owls that observe that funky behavior experimentally.)

Just like your poor fellows out west, just fix your old-school clocks before going to bed, and go to sleep early, it's good for you.

Rest of the world with DST

Renewed and recurring apologies again to the people of Cuba, Mexico, Moldova, Israel, Lebanon, Palestine, Egypt, Chile (except Magallanes Region), parts of Australia, and New Zealand which all have their own individual DST rules, omitted here for brevity.

In general, changes also happen in March, but either on different times or different days, except in the south hemisphere, where they happen in April.

Rest of the world without DST

All of you other folks without DST, rejoice! Thank you for reminding us how manage calendars and clocks normally. Sometimes, doing nothing is precisely the right thing to do. You're an inspiration for us all.

Changes since last time

There were, again, no changes since last year on daylight savings that I'm aware of. It seems the US congress debating switching to a "half-daylight" time zone which is an half-baked idea that I should have expected from the current USA politics.

The plan is to, say, switch from "Eastern is UTC-4 in the summer" to "Eastern is UTC-4.5". The bill also proposes to do this 90 days after enactment, which is dangerously optimistic about our capacity at deploying any significant change in human society.

In general, I rely on the Wikipedia time nerds for this and Paul Eggert which seems to singlehandledly be keeping everything in order for all of us, on the tz-announce mailing list.

This time, I've also looked at the tz mailing list which is where I learned about the congress bill.

If your country has changed time and no one above noticed, now would be an extremely late time to do something about this, typically writing to the above list. (Incredibly, I need to write to the list because of this post.)

One thing that did change since last year is that I've implemented what I hope to be a robust calendar for this, which was surprisingly tricky.

If you have access to our Nextcloud, it should be visible under the heading "Daylight saving times". If you don't, you can access it using this direct link.

The procedures around how this calendar was created, how this email was written, and curses found along the way, are also documented in this wiki page, if someone ever needs to pick up the Time Lord duty.