Re: Feb 29, 2000

I just gotta ask...

How is it that people in 1582 could figure out that an earth year was 365.2422
days long?  How did they measure it with that precision?  By using 1/10000 day
precision, we're talking 8.64 seconds per _year_.

They eliminated 10 days off the calendar in October 1582.  Based on what
measurement?

BTW, IBM date data type accepts 10/10/1582 as a valid date.  Maybe we should ask
them to fix that???  <g>

So many questions...

- Dan Bale

________________________ Original Messages ___________________________

From: dhandy@isgroup.net (Douglas Handy)
Subject: Re: [Feb 29, 2000]

>The Gregorian calendar had just been introduced that century(!?!? or was
>it the one before?)

According to Paul Conte's infamous date routines, the dates skipped
were Oct 5, 1582 thru Oct 14, 1582.  It could be noted that his
routines ("The Last Date Routines You'll Ever Need") return these as
invalid dates.

------------------------------

Date: Thu, 30 Sep 1999 10:23 +0700
From: "Harry D. Angkasa" <harry@bngtw.bniaga.co.id>
Subject: Re: Feb 29, 2000

     The Sun goes around the globe are 365.2422 days. To make it easier
     Gregorius made 365 for a year. For February, he made 28 days for
     February, and 29 days for every 4 years to make correction. The
     average days for 4 years would be (365+365+365+366)/4 = 365.25 days
     per year. It is not so accurate, isn't it? .
     That is why he made another rule :
     - 365 days for every 100 years, even though it can be divide by 4.
     - 366 days for every 400 years.
     That rule will make a correction of minus 3 days for every 400 years,
     or -3/400 = -0.0075. With this correction, 1 year become 365.25 -
     0.0075 = 365.2425

     He ignored the different value of 0.0003 days.

------------------------------

From  The Origin of Leap Year

Pope Gregory XIII took action in the year 1582 by
cutting 10 days off the month of October and devising
the Gregorian Calendar, the one we still use today.
The last day of the Julian Calendar was Thursday,
October 4th, 1582, followed by Friday, October 15th,
1582. Clavius' solution was to make no Centennial
Year a leap year unless it was divisible by 400. Since
1600 was coming up, it was noted that it would be a leap
year, whereas 1700, 1800 and 1900 would not. The year
2000 will be a Centennial Leap Year. He also realized
that this solution slightly overcorrected the calendar.
Therefore, any year that is divisible by 4,000 would be
called a Common Year and would not be a leap year.
This has the effect of bringing the calendar back in line.
There will not be a Common Centennial Year until the
year 4000.





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