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Dec 25, 2002, 6:59pm

The 24h time notation specified here has already been the de-facto standard
all over the world in written language for decades. The only exception are a
few English speaking countries, where still notations with hours between 1
and 12 and additions like "a.m." and "p.m." are in wide use. The common 24h
international standard notation is widely used now even in England (e.g. at
airports, cinemas, bus/train timetables, etc.). Most other languages don't
even have abbreviations like "a.m." and "p.m." and the 12h notation is
certainly hardly ever used on Continental Europe to write or display a time.
Even in the U.S., the military and computer programmers have been using the
24h notation for a long time.

The old English 12h notation has many disadvantages like:

It is longer than the normal 24h notation.
It takes somewhat more time for humans to compare two times in 12h notation.
It is not clear, how 00:00, 12:00 and 24:00 are represented. Even
encyclopedias and style manuals contain contradicting descriptions and a
common quick fix seems to be to avoid "12:00 a.m./p.m." altogether and write
"noon", "midnight", or "12:01 a.m./p.m." instead, although the word
"midnight" still does not distinguish between 00:00 and 24:00 (midnight at
the start or end of a given day).
It makes people often believe that the next day starts at the overflow from
"12:59 a.m." to "1:00 a.m.", which is a common problem not only when people
try to program the timer of VCRs shortly after midnight.
It is not easily comparable with a string compare operation.
It is not immediately clear for the unaware, whether the time between "12:00
a.m./p.m." and "1:00 a.m./p.m." starts at 00:00 or at 12:00, i.e. the
English 12h notation is more difficult to understand.
Please consider the 12h time to be a relic from the dark ages when Roman
numerals were used, the number zero had not yet been invented and analog
clocks were the only known form of displaying a time. Please avoid using it
today, especially in technical applications! Even in the U.S., the widely
respected Chicago Manual of Style now recommends using the international
standard time notation in publications.


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