# 24-hour clock

On a 24-hour digital clock, is 23:59:59 followed by 24:00:00, or by 00:00:00?

My clock shows 00:00. Looks funny.

00:00:00. The hours are 0 to 23.

Exactly. The prior day ended at 23 hours, 59 minutes, and 59 seconds. 00:00:00 is a reset of the 24-clock, an establishment of a new day. If it reads 00:00:01, that means it is 1 second PLUS some time into the new day.

If it were 24:00:00 that would insinuate that at least the first second of the new day was still on the previous day.

Actually, 00:00:00, not 23:59:59, ends one day and begins the next. It’s a dividing point.

Are you suggesting that if something occurs at 00:00:00 then you cannot say what date it occurred on because it is the dividing point between two days?

Most normal people convert 00:00:00 to midnight or 12:00 a.m. which is the subsequent date. Aug. 1 becomes Aug. 2 at 00:00:00 so seems like 00:00:00

00:00:00 has no duration; it is a point. Because it has no duration, nothing can “occur” only at that point. 23:59:59 to 00:00:00 is one second; 00:00:00 to 00:00:01 is one second. But 00:00:00 has no duration. Just like in geometry, where a point has no length.

What did I say that was different?

23:59:59 is the last second of the previous day, 00:00:00 begins the first second of the new day.

You’re wrong. 00:00:00 has a duration of one second.

The clock doesn’t go from 23:59:59 to 00:00:01, just like it doesn’t go from 23:59 to 00:01 or 23:00 to 01:00.

You must be using schroedinger’s watch.

Digital clocks invariably change from 23:59:59 to 00:00:00 but I have seen 24:00 in train timetables as an arrival time:

23:35 dep. A-city
24:00 arr. B-town
00:00 dep. B-town
00:45 arr. C-town

I just wanted to point out that 24-hour clocks are for the uneducated, stupid, God-humans..

Tripler
And ‘Dr.’ Gene Ray will debate you on it, too!

Dude, what the hell was that?!?

I had heard that someone (Einstein?) had also said that exact noon and midnight weren’t “real” times. Any help on that?

Hmm. I don’t know about the link, and I’m not sure I want to, life being short and all that.

As to times, well, I dunno. Why would we assert that 00:00:00 is less of a “real” time than “14:21:53”? I suppose (without any real knowledge) that it could be asserted that time isn’t fixed, but relative. But for those of us living normal lives in the real world, we may find that when we show up late for work, our boss will be unimpressed by a claim that we weren’t really late because time is not an immutable measure.

I tend to think it had one second left at the instant that appears. It ends (and a new day starts) at the instant when “00:00:00” appears on the clock. You are quite right that this indication, like all others, stays on the clock for a full second.

I have heard that a few years ago some computers could not cope with the concept of midnight expressed as 00.00.00. As an example this caused problems to a cross-channel ferry operator who had a scheduled sailing at midnight and to those people who wanted to book a ticket electronically. To get round this the actual advertised time for this boat was 23.59.00

When I was in the USAF 2400 was midnight, the next minute was 0001.00

In German, 00:00:00 is called “Null Uhr” which translates as “Zero Hour” or “Zero o’clock”…I always found it kind of funny to say.
It was especially weird when it was 12:30 AM and you would say it is “Null Uhr dreizig” (zero hour thirty).
Took awhile for my American trained brain to get used to saying that.

Actually, it’s either way, depending on the activity and it’s duration. . .

If the mess hall is open from 2000 until 2400 on Wednesday, it’s open Wednesday night from 8:PM to 12:AM. If it’s open for breakfast at 0000 to 0400, it’s open from 12:AM to 4:AM in the morning.

It’s all a matter of context, but it’s sometimes done for ease of math (when figuring out durations) or just to make a point.

Tripler
And if you’re eating breakfast that early, I am truly sorry.

Yeah, I remember the AF doing that as well and it never made a whole lot of sense to me.