Comments on Spotting the ISO calendar

Karl (2003-12-04T09:22:23Z)

The set of years that have 53 ISO weeks is asymmetrical. There exists no Y (integer or half integer), so that year Y+X has the same number of ISO weeks as year Y-X, for all X.

Each year of 53 ISO weeks comes either 5 or 6 years after the previous such year with one exception every 400 years.

If ISO weeks were defined be begin on Sunday instead of Monday, then the number of ISO weeks in year 2000+X would equal to the number of ISO weeks in 2000-X. In other words, the set of years with 53 weeks is symmetrical about the year 2000. This only works with weeks beginning Sunday. Here are some examples:

1980, 1986, 1992, 1997, 2003, 2008, 2014, 2020.

Karl (2003-12-04T09:06:04Z)

Years ago (in 1998), I thought of a way of naming the 52 or 53 ISO weeks after playing cards. The suits form seasons: Clubs ISO weeks 1-13
Diamonds ISO weeks 14-26
Hearts ISO weeks 27-39
Spades ISO weeks 40-52
Joker ISO week 53

Today is Thursday ISO week 49, so is Thursday, Ten of Spades.

See http://www.hermetic.ch/cal_stud/palmen/playcard.htm

clipper (2003-12-03T14:49:21Z)

Dans le monde de l'entreprise, et en particulier entre deux entreprises, quand il s'agit de fixer une réunion, un diner, whatever, le numéro de semaine est très utilisé.


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