Message-Id: <MAILQUEUE2-102.931006224146.384@hylkn1.Helsinki.FI>
Date:         Thu, 7 Oct 1993 09:48:10 GMT+1200
Reply-To: Chris Handley <CHandley@gandalf.otago.ac.nz>
Sender: vilva
From: Chris Handley <CHandley@gandalf.otago.ac.nz>
Organization: University of Otago
Subject:      Re: local units
To: Veijo Vilva <VILVA@viikki21.helsinki.fi>
Content-Length: 1371
Lines: 28

John Cowan:

>        1 gigasecond = 31 years 251 days 13 hours 34 minutes 51.52 seconds
>                                                                ^^?
>(assuming all years are 365.2422 days long exactly).

The _tropical_year (which is the one we use because it stays in time with
the seasons) is measured as 365.24219 (or 365.24220 depending on which
reference you choose) is usually _defined_ as 31,556,926 seconds. (In fact,
for some time the second was defined as that part of the year 1900, until
more modern methods took over). Every so often a leap second is added, to
allow for inaccuracies in measurement, changes in the speeds of rotation and
revolution, etc.

BTW, the current method of specifying leap years (+1/4 -1/100 +1/400
-1/4000) is accurate for about 20,000 years. An alternative would be (+1/4 -
1/128) is accurate for about 400,000 years. Which is 'better'?


======================================================================
Chris Handley                                     chandley@otago.ac.nz
Dept of Computer Science                       Ph     (+64) 3-479-8499
University of Otago                           Fax     (+64) 3-479-8577
Dunedin, NZ
______________________________________________________________________
              There are three types of Computer Scientist:
                those who can count and those who can't.