Re: [LEAPSECS] civil time = solar time

From: William Thompson <William.T.Thompson.1_at_GSFC.NASA.GOV>
Date: Thu, 05 Jan 2006 17:18:55 -0500

Clive D.W. Feather wrote:
> Rob Seaman said:
>>Rather, the often repeated canard that civilians don't give a fig for
>>the actual position of the sun in the sky implies that it is
>>precisely apparent solar time that only queer ducks like astronomers
>>care about. Mean solar time is what civilians DO care about.
> Only *very* *very* approximately.
> In the UK, sunset varies from about 15:30 to about 22:30 LCT. Sunrise isn't
> an event most people even care about (for me, it shifts from "happens at
> work" to "happens before I get up" on an annual basis but, during the
> winter, on a weekly basis as well).
> Provided that astronomical noon is between about 08:00 and 16:00, most
> people won't care.

People certainly seem to care in this country (USA). There's always a lot of
discussion about it when shifting between standard and daylight savings time,
and especially when discussing the date on which that switch should take place.
  The biggest effect that people seem to be worried about is whether the Sun
will be up when children are going to school in the morning.

Similarly, many people with small farms also have other jobs, and have to
complete their chores in the morning before going off to work. To them it's
very important what time the Sun comes up. I have this on good authority from
one of my colleagues who is in just this situation. It's also figured in
discussions about DST in the media.

Finally, there's a very good reason why politicians spend so much time worrying
about DST--there's a distinct impact on the economy, especially in terms of
energy use.

People definitely care about the relationship between civilian time and apparent
solar time. The amount of fiddling with the dates of DST to get it "just right"
tells me that people care about apparent solar time to somewhat better than one
hour accuracy.

William Thompson
NASA Goddard Space Flight Center
Code 612.1
Greenbelt, MD  20771
Received on Thu Jan 05 2006 - 14:19:14 PST

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