Thanks, Bill. I don't recall mentioning 24:00, but I agree with what you wrote in USMA 17129. However, I would add that 24 lasts for only one second; 24:00:01 is not valid. Hence it would be very complicated to construct a clock that would show 24:00
>As Joe Reid (I think) has pointed out, it depends on the context. > >Although 24-hour clocks don't display 24:00, expressing midnight as 24:00 is >explicitly permitted by ISO 8601:1988 as an alternative to 00:00 -- in >emphasizing the completion of one day, for example, rather than the >beginning of the next. > >I haven't checked ISO 8601:2000, as I don't have a copy. However, Markus >Kuhn's web site (accessible from http://metric1.org/dateandtime.htm) >contains the following: > >As every day both starts and ends with midnight, the two notations 00:00 and >24:00 are available to distinguish the two midnights that can be associated >with one date. This means that the following two notations refer to exactly >the same point in time: > >1995-02-04 24:00 = 1995-02-05 00:00 > >In case an unambiguous representation of time is required, 00:00 is usually >the preferred notation for midnight and not 24:00. Digital clocks display >00:00 and not 24:00. > >Bill Potts, CMS Joseph B.Reid 17 Glebe Road West Toronto M5P 1C8 TEL. 416-486-6071
