Melanie Baillot (1:163/215) schreef aan Arun Jayaprakash op 01-Mar-99 om 19:27:

 MB> Can someone explain why they just can't do it from 1000 to 9999 

You still have only about 100 years range in the year (it IS only 7 bits, so a
0-127 value).

 MB> ?? There must be some mathematical thing to calculate at what day 
 MB> the begining of a year starts etc...

Not really, especially with the various (in different countries) calendar
reforms. Essentially you just calculate out the number of days difference
(modulus 7) between the date you want the day OF and a reference date you KNOW
what day it was. In this you have to account for leap years etc.
And, of course, the "being a leap year" of the centuries depend on which
country you are doing it for, the calendar reform in which 1700/1800/1900
became NON-leap years was proclaimed (by the pope) in the 16th century, but
Protestant countries like the UK and the USA didn't implement it until the 18th
and for instance Russia only implemented it this century.
So in France and Italy 1700 was NOT a leap year but in the USA it was.

In my own country (The Netherlands, at that time the Republic of the 7 United
Provinces) it was even different per province when the calendar reform was
really implemented.

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