Re: Time

On 2007-03-07, Engineer <invalid@xxxxxxxxxxx> wrote:
Does anyone know of evidence that any ancient civilization
set the time when the day changes in the middle of the night?

I doubt if anyone /knows/ a definitive absolute answer to that question.

Most cultures in the past, and some today (most noticeably observant Jews
and Moslems) have used sun-rise or sun-set to mark the change of date.

Common parlance in my experience seems to be to use 'tomorrow' to mean
'after I've slept and woken up again'. TV and radio listings often include
programs for 'a few hours' after midnight as part of today rather than
tomorrow; the leading listings magazine here in the UK is "Radio Times",
which seems to start each day's lists at 6 AM local time for TV but
anything from 5 to 7 AM for radio stations.

Astronomers found it convenient to have the date change at some time that
wasn't dark; so they could manage well enough with either the sun-rise or
the sun-set change-over - but for the easiest compilation of astronomical
tables, 'equal hours' and a date-change that happens at some time that
doesn't change with the seasons and latitude, is the most convenient
arrangement. Mid-day is the obvious choice and that is how things were
until quite recently - for astronomers. Of course, mid-day at which
longitude is another point of dispute ;))

"GMT" as used in old astronomical tables, star charts, ephemerides,
navigation charts, etc, used to have 0000 hours at Greenwich mid-day; I
think the switch to having 0000 hours at Greenwich mid-night took place in
the early 20th century (the date 1915 sticks in my mind, but I haven't
managed to pin it down on-line).

Interesting links:

<http://wwp.greenwichmeantime.com/info/time-zones-history.htm> (yes, wwp)
<http://www.maa.mhn.de/Scholar/times.html>
<http://www.ecben.net/calendar.shtml>

(Some of the links inside those pages seem to be broken).

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~
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