week starts at Sunday or Monday??

Markus Kuhn Markus.Kuhn at cl.cam.ac.uk
Wed Oct 4 09:17:40 UTC 2000

"Infoman Inc." wrote on 2000-10-03 21:18 UTC:
> "and on the seventh day, ye shall rest"   for Gregorian calendar =Sunday,
> for Hebraic, Seventh Day Adventists (and others) = Saturday, etc.

On the other hand, in some languages (e.g., German: "Mittwoch"), the
word for Wednesday means literally "middle of the week", which would
imply a week-start of Sunday.

Unfortunately, I have never seen a proper written rationale for the
decision of ISO to declare in ISO 2015:1976 "Numbering of weeks"
(withdrawn by TC154 on 1988-06-01 and now superseded by ISO 8601) that
the week starts on Monday. Annex A of ISO 8601:1988 just says that
before that, various week conventions were in use in various countries
and that starting on Monday was considered to be the commercially most
useful convention for selecting an international standard. Does anyone
have a copy of ISO 2015:1976 that might contain a more detailed

I do vaguely remember that I have read many years ago in a German
publication for hobby astronomers a good article on the ISO week
numbering standard. It said something along the lines that workers find
it more convenient of weekly shift rotations start during the night from
Sunday to Monday, because most people prefer to have a complete weekend
before a shift change. Therefore, it seemed most compatible with
industrial planning practice to start the new week on Monday as then
shift rotations would correspond exactly to the week number. There were
similar reasons for accounting practice in 24x7 operations and for the
idea of making week 1 the first week with the majority of the days in
the new year (to avoid pathologic partial weeks at the beginning and end
of most years). The article also mentioned some protest by the churches
in Germany, when around 1977 the DIN standard for calendar dates was
changed to the new ISO convention and printed calendars started to
show Monday as the first day of the week accordingly.


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org,  WWW: <http://www.cl.cam.ac.uk/~mgk25/>

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