24 hour clock

[ianess]

On the 24 hour clock exactly what time is meant by 0000hrs?   Is it for example midnight Friday before Saturday or midnight Saturday before Sunday?

To avoid ambiguity I was always taught to use 0001 or 2359 but what say others? 

[Skids]

0000hrs is generally taken to be the start of the day, hence its all zeros and not 2400hrs. So 0000hrs on Saturday would be Friday night/Saturday morning. For the purpose of watch-keeping, the Royal Navy does not recognise 0000hrs. Instead 2359 lasts for a minute and a half, as does 0001. However, should something happen at 0000 then it gets logged at 0000. This is when 0000hrs being at the start of the day comes in.

[ianess]

Good answer Skids and one that I can totally agree with, the fact that zero comes before one.

By using the same logic does that mean that 2400hrs does not exist? We simply jump from 23.59.59 to 00.00.00?

[smudge]

When I used to do the payroll for the night shift, I always took 00:00 to be midnighht & 00:01 as the start of the next day.

[bonusboy]

The same conundrum applies to 12-hour times, btw.  What time is 12:00AM ?  Or 12:00PM?  I just use 'midnight' or 'midday' instead

[IndieSinger]

There has never been any doubt in my mind - both 12:00am and 00:00 are the beginning of the new day. (12:00pm is 12:00 on the 24-hour clock and 24:00 doesn't exist (and never has)).

[anthomson]

00:00 hours is of course both the end of one day and the beginning of the next since this must happen at a single moment of time. To say one happens a minute before the other does not make sense. I am currently doing a project for the NHS where we are not allowed to accept 00:00 as a valid time but suspect the reason for this is that 00:00 may be confused with 'time not known'

[greenday]

It always been fairly clear to me that 00:00 (or mid-night) is the start of the new day. Note this comes one second after 23:59:59, and is not the same instant. No instant in time can possibly be two different days, it's either one or the other. For New Year's celebrations I always go by that as does everyone else in the world apparently.

[hovnav]

As you may see my code name is  '  hovnav '  which is abbreviation for hovercraft navigator (ex RN)  and although not a complete expert I agree with most of the the answers, including the reference to the Royal Navy. But my last teaching was that you log a time of 23.59.59 and then 00.01.01 and we were taught never to log a time of 00.00.

There must be a reference to all this on the Royal Observatory Geenwich site and the place is well worth a visit,(small charge). Along with the National Maritime Museum. ( free ! ) This year a special Nelson bicentenury display and a  ' must-discover '  the most important timekeeper ever made by a man called Harrison, (1759) .  And,no, I do not work there !

                                                           hovnav

[Fitzburger]

0000hrs or 00:00 is midnight

1200hrs or 12:00 is midday, time to put the kettle on.

NB: Most Americans aren't taught about the 24 hour clock until they are about 15. its just too difficult a concept to grasp