So we're on our way back to standard time

The clocks turn back at 1:59AM meaning we go from 1:00AM to 1:59AM twice tonight.

Suppose something really important happens between now and then - let’s say at 1:37AM. How will history record which 1:37AM the important event occurred?

Easy, record the time in GMT.

Since as far as I know there is no precedent for this, let’s move this to IMHO.

General Questions Moderator

My guess is that Standard Time for the locality would take precedence. If it was important, one would have to specify (for example) EST vs. EDT.

You have lots of options.

Suppose you’re in the Eastern Time Zone of the US, observing Daylight Saving Time. Right now (a few hours to go before the switchover), our clocks are all set to EDT = Easter Daylight Time. After the switchover, all our clocks will be set to EST = Eastern Standard Time. The former is defined at UTC-4 and the latter is defined as UTC-5. UTC (Coordinated Universal Time) is not subject to Daylight Saving Time. It clicks along steadily in all four seasons, except for the occasional leap second to keep it synchronized with UT1.

Suppose that, 23 minutes before the switchover, you hear a loud bang outside your bedroom window, look at your clock, and see that it says 1:37 AM.
At this moment, your clock is set to EDT.
You could say any of the following:
I heard a loud bang at 1:37 AM EDT.
I heard a loud bang at 12:37 AM EST.
I heard a loud bang at 05:37 UTC.
All three of those statements are accurate and none of them are ambiguous.

Suppose, exactly one hour later, a police car pulls up in front of your house with its lights flashing.
If your clock is connected to the internet, it probably adjusted itself automatically and now is on EST.
You could say any of the following:
I saw the police car at 2:37 AM EDT.
I saw the police car at 1:37 AM EST.
I saw the police car at 06:37 UTC.
Again, all three of those statements are accurate and none of them are ambiguous.

The only way it’s ambiguous is if you just say “It was 1:37 AM” or “My clock said 1:37.”

FWIW, UTC is often referred to colloquially as “GMT”. Military or aircraft often refer to it as “Zulu time”.

Don’t the local times have time zone designations like here we have AEST and ADST - Australian Eastern Standard Time and Australian Daylight Standard Time.

I have not lived in a place that changes its clocks since 1991.

Yes. As I mentioned, Eastern Standard Time (EST) is distinguished from Eastern Daylight Time (EDT).

^ This
It is not that hard to translate GMT to local time. I do dislike the time changes here in the US, but I tend to ignore it unless I have sort of appointment.

It’s just me, but my biological clock adjusts quite nicely. Sunrise and Sunset arrive precisely as predicted. It is my $50 Timex wrist watch that needs a spanking. :smiley:

Actually, there is plenty of precedent, as we have been using Daylight Saving (here in much of the US, anyway) as the Official Time for over half a century. There are plenty of records where the actual time has legal implications, and the time zone designation (either EST or EDT, per your own post) is a part of the the notation.

I am not surprised more people do not understand this. If you talk to normal, seemingly intelligent people about it, they start acting like moon landing deniers. Nearly everyone I have met that lives in Eastern Time zone believes that Eastern Standard Time is called that because it is the standard the country runs on (or, at least, should run on).

Living in the Central Time zone, I learned when making plans with an ETer for a phone conference, or similar, and they suggest a time of, say, 3PM EST, I ask them if that is Daylight Saving or Standard time, they get flustered and just say “Three in the afternoon, MY TIME!”. Of course, 3PM EST is the same as 3PM CDT, and there are (used to be, anyway) some folks in Indiana who didn’t do the EDT thing, so the distinction is not trivial.

Are you going to move the thread back to GQ next spring?

So is that when the bunnies come out?

Of course, I was referring to something of historical importance happening in the hour of transition between Standard and Daylight Time. .

But you’re right, there is a routine way to distinguish between times in the two systems.

I live in Panama, which like the rest of the tropics doesn’t go on Daylight Time. We are on EST (actually Bogota time) all year. I just have to keep track of when people in Eastern Time are an hour later than me.

It was annoying during the baseball playoffs, because some websites give the local time when the games start, and some are automatically adjusted to my local time. It can be very confusing when they don’t indicate the actual time zone they are giving the time for.

For more clock adjustment silliness, due to the Energy Policy Act of 2005, daylight saving time was extended in the United States beginning in 2007. This has created an interesting situation for those of us who program in .NET. The DateTime struct in .NET assumes for US time zones that the Energy Policy Act of 2005 has always been the case. The original “spring forward” date to DST was the first Sunday in April. Under the new act it was moved to the second Sunday in March. During that morning of the time change, there is no 1:00 hour. The time goes from 12:59:59 to 2:00:00. Now imagine you have a timestamp in a document that was recorded during the 1:00AM hour on the second Sunday of March prior to 2007. If you try to initialize a DateTime structure object to that value, an exception is thrown that it is not a valid value.

I ran into this situation last week. It took me a few minutes of banging my head into my desk trying to figure out what I was doing wrong until I realized that the timestamp I was reading in was the problem, not my code.

“At 1:37 EDT, Dodgy Dude was run over by a bus. He expired from his injuries an hour later, at 1:37 EST”.