week starts at Sunday or Monday??

Martin Smoot msmoot at nssolutions.com
Tue Oct 3 15:38:07 UTC 2000

Most pre-printed calendars that I have seen in the United States show
Sunday as the first day of the week.  I think I have seen "specialty"
calendars that have Monday as the first day but these are obviously an

The "Zeller's Congruence" algorithm as normally presented uses Sunday as
the first day of the week.  One site
(http://serendipity.magnet.ch/hermetic/cal_stud/newman.htm) presents a
draft specification that contains a subroutine based on this algorithm
at the end of the page and assumes Sunday is zero.  There is also a
reference to the timezone data site in this draft.  This page references
an out of date FTP page but I suspect that there is an official page
already (I have not bothered to look for it).

I saw another page from 1996 that presented the algorithm as part of a
programming contest (http://www.sandusky.k12.mi.us/cs96_1.htm - problem
4) and presented essentially the same algorithm.

The http://www.merlyn.demon.co.uk/moredate.htm page has the following:


The Start of the Week

Traditionally, at least for the English, the week starts on Sunday,
which is the Holy Day and the first day of the seven,
numbered "one". 

Others have different Holy Days, perhaps at the end of their week, but
generally occurring on the English days Friday or
Saturday, and with their own choice of starting and finishing times. 

The International Standards Organisation, in ISO-8601, prefers to start
the week later, with day one being Monday.
British Standards agree. 

Normally, the day numbers are considered ordinal, from the first to the
seventh, as is the case for the days of the month.
But some prefer cardinals, with the days being numbered 0..6 in


Perhaps a "Zeller's Congruence" based set of routines following the ISO
standard would be useful....
Martin Smoot
Network Storage Solutions
msmoot at nssolutions.com         www.nssolutions.com

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