Noon and midnight

Subject: Noon and midnight
From: DAVID IBBETSON <ibbetson -at- IDIRECT -dot- COM>
Date: Thu, 15 Aug 1996 11:19:41 -0400

We seem to be getting into a discussion of the difference between mean- or
clock-time and sun- or sundial-time. The difference can be as much as 20
minutes. Or have I missed something? (Please don't further complicate the
issue by bringing in daylight saving time and the difference in sun-time
between the two edges of a 15 degree time zone. I hope these are irrelevant.

Noon and midnight are instants. Noon is neither before nor after itself.
Midnight belongs to neither the old nor the new day.

However digital clocks that display time to the nearest minute change their
indicator from am to pm at noon. This is reasonable because the subsequent
minute (until the clock shows 12:01pm) is already _after_ noon. Somilarly
for midnight.

If you use the 24 hour clock you have a choice between calling midnight
2400hrs on Friday or 0000hrs on Saturday. For mechanical reasons digital
clocks are more likely to use 0000hrs but, as I noted before, some people
use 2359 Friday or 0001 Saturday to avoid confusion.

I hope this helps, but the definition of an instant of time, like the
definition of a point is mathematics and this seems to frighten some people.
(The definition of a point is one of Euclid's axioms. He says it has no size.)

David (the mathematical idiot) Ibbetson


David Ibbetson ibbetson -at- idirect -dot- com
133 Wilton St, #506, Toronto, Ontario, Canada M5A 4A4
Phone (416) 363-6692 Fax (416) 363-4987

Fiat justitia et pereat mundus (Let justice be done, though the world
perish) -- Motto of Ferdinand I (1503-64), Holy Roman Emperor from 1558
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