Re: [LEAPSECS] civil time = solar time

From: Poul-Henning Kamp <>
Date: Thu, 05 Jan 2006 08:18:11 +0100

In message <>, Rob Seaman writes:

>I said:
>> all parties must certainly agree that civil time (as we know it) IS
>> mean solar time.
>Ed says:
>> saying that it "IS" civil time is probably a bit strong.
>"Probably a bit strong" is not precisely a staunch denial.
>This is simply a classic exercise in applying epsilon constraints.

Yes, another inappropriate method used to sell your bogus argument.

It's bogus because neither "local time" nor "civil time" is a
continous variable but a quantified variable (because of the timezones)

The minimum epsilon constraint which is valid for a quantified
variable is the unit of quantum. That is why all digital measurements
by definition have an uncertainty of at least +/- 1 digit.

The longitude conference defined the unit of quantum as 1 hour but
despite this I belive a few localities (.au ?) have opted for a
30minute quantum.

>> 1. local civil time matches apparent solar time roughly

Because local civil time have chosen timezones appropriate for
this purpose.

>> 2. the relationship between local civil time and apparent solar
>> time is constant enough in any one place

Uhm no. Politicians have decided to make it flip 15 degrees forth
and back with summertime regulations.

>> 3. the rate of local civil time is constant at least to the
>> precision of most clocks and watches.

This is a rather empty statement because most clocks and watches
are built, sold, bought and adjusted to show civil time.

>> 4. the relationship between local civil time and international
>> civil time should be predicatable and easy to calculate with

Which is why the longitude conference decided on a 1 hour quantum.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Received on Wed Jan 04 2006 - 23:28:44 PST

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