Interesting factode - bank DD's

[Scion]

Tim Streater put finger to keyboard:

True, although 24:00 is used to denote exactly the start of 00:00 the following day.

For example in car insurance, if your old policy runs out on 30/01/15 at

23:59 and the new one starts on 31/01/15 at 0:00 then what's the score on the 30th at 23:59 and 30 seconds? Saying the old policy expires on 30/01/15 at 24:00 is intended to clarify that the extra minute between 23:59 and 00:00 is indeed covered. I would argue that there are better and clearer ways of communicating that fact, but there you have it.

[Adrian]

23:59 includes 23:59:00 to 23:59.9999999

As soon as 23:59 finishes, it's 00:00 - so the exact point at which the old policy expires is the exact point at which the new one starts.

Gawd knows what happens if - just on the stroke of midnight - your car is just bouncing out-of-control off a bus towards the queue of nuns carrying baskets of kittens.

[Mike Barnes]

2400 is a useful shorthand for 0000 the next day, especially if it's indicating the end of a time period.

Some continental no-parking signs are qualified by '0-24', which IMO is much better than our 'AT ANY TIME'. Not that there's any need for either of them IMO... no parking is no parking.

[Chris French]

Yes, our Smile account is similar, they say we can pay in money on the same day as long as it is available by 16:30.

[Mike Clarke]

No, they're both today. I'm typing this at 15:47 so 00:00 was 15 hours and 47 minutes ago as the clock ticked past midnight at the start of today and 24:00 will be 9 hours and 13 minutes later at the end of today.

[Scion]

Adrian put finger to keyboard:

Or you prang your car at 23:55, park it legally at the side of the road, inform your insurer before midnight, and some muppet (or a nun with a basket of kittens) smacks into the back of it at 00:05.

[Robin]

yes, well, the first was supposed to 31/12/14 24:00:00

Isn't 24:00:00 accepted under ISO8601 in order to avoid confusion about midnight? For example if the pub only has a license until midnight on Sunday it's clearer to give chucking out time as 24:00:00 Sunday rather than 00:00:00 Monday?

[Johny B Good]

Er, which _one_? That's a 2 minute interval you're describing so a fuller answer to that ill formed question would be, "The last minute of the previous day, immediately followed by the first minute of the next day.".

I guess the banks are zerophobic so specify the one minute past the start of the day to put it beyond reach of confusion that any future sloppy re- interpretations of when a day finishes and the next day starts.

Logically, 23:59 is a truncated representation of the final minute of the day. Similarly, 23:59:59 is a truncated representation of the final second of the day when 'to the second' precision is demanded.

The starting time for each day, logically, should always be 00:00 which, likewise, is merely a truncated representation of the first minute of the day.

[Adrian]

23:59:59 (end of 23:59) xx:xx:00 ... xx:xx:59 00:01:00 (start of 00:01)

Exactly sixty seconds between the end of 23:59 and the start of 00:01

[Tim Streater]

I think you mean (not sure why you put the xxes in so I corrected that for you):

23:59:59 (end of 23:59) // and one second later, we have: 00:00:00 ... 00:00:59 // and one second later, we have: 00:01:00 (start of 00:01)

But when the clock ticks over to 23:59, and when the clock ticks over to 00:01, that *is* a two-minute interval.

[Adrian]

Because this whole subthread is a debate about what to call those sixty seconds...

Well, yes. But one of those minutes is 23:59 - which isn't being debated. It's one minute between 23:59 ending and 00:01 starting.

[Mike Barnes]

Far be it from me to stop anyone bickering, but...

I think the two of you are tripping over the fact that hh:mm can either mean a point in time or an interval of one minute, and it's often not clear which. Clearly the questioner meant the point in time rather than the interval. The interval would have been two minutes if had he meant the interval, but he didn't.

[Adrian]

You know that, I know that...

[Adrian]

Nah, we're agreeing vehemently.

[Tim Streater]

Sure. But then it depends how you write it. I can have an interval of

75 mins, but then I wouldn't write that as 0:75. I'd write it as 1:15 (note the lack of leading zero since it's an interval, not a wall clock time).

[Bob Eager]

Anyway, I thought factode was where you mined factoids...

[Robin]

When it comes to law UK statutes have happily used 24:00 for many years (usually when giving effect to EU Directives). Eg SI 2002/3117 tells you "Each 8-hour average so calculated shall be assigned to the day on which it ends, i.e. the first calculation period for any one day shall be the period from 17:00 on the previous day to 01:00 on that day; the last calculation period for any one day shall be the period from 16:00 to 24:00 on that day." There's nothing in the Interpretation Act on this but I'd expect common usage - backed up by ISO8601 - would be enough for any judge.

[Johny B Good]

Interesting. :-) I'm wondering at which point do you insert the 'leap minute' required to correct for this two minute jump?

Don't forget, when it comes to _representing_ the time of day on a four digit display, it's simply not possible to represent that infinitesmally small instance in time when the clock increments the minutes back to 00, generating a carry into the hours counter which then generates a carry into the days counter (whether it exists or not in the clock mechanism) when resetting back to all zeroes to display the fact that the time period is within the first minute of the next day.

Unfortunately, even measuring to billionths of a second resolution doesn't overcome this 'problem'. Time is an 'analogue' quantity that we note or record in quantum increments. Even supposing the existence of 'time quanta' as proposed by some researchers, this is more likely to arise from using a system limited by the quantum behaviour of atoms used in the construction of such a quantum clock.

IOW, to paraphrase Terry Pratchett, "It's analogue all the way down!". :-)

[Johny B Good]

Ah! At last, someone else has noted the malapropism in the subject line. :-)

[Johny B Good]

Interesting uses for recording that special time at the end of a day as 24:00 which no 4 digit clock will ever display (see the top and bottom entries of the table for why). These are more a matter of 'convenience' than strict logic.

A clock has to follow strict logic in order to function. You cannot display both 00:00 _and_ 24:00 simultaneously on a digital clock display. This leaves you with the choice of either starting the day at

00:01 and ending at 24:00 or, more correctly, starting at 00:00 and ending with 23:59 before wrapping back round to 00:00 again for the start of the next day.

Since the display can only report an event that immediately becomes an historic fact by the femtosecond for the next 60 second time interval in the case of a 4 digit display, it makes perfect sense to never use the 00:01 through to 24:00 range to represent the time of any one day.

It's this wooly minded reasoning based on convenience for the specific examples where a time of 24:00 is referenced that scares the banks shitless into 'steering clear' of this troublesome zeroeth minute of the day.