Christoph Bugel wrote:

so my question is.... now that I decided that days are niumbere 1 to 7, what is day 1 ??? is it Sunday, or Monday? what is the Right Thing to do?

The document by Gary Houston describing the ISO 8601:1988 date/time representations that is available at ftp://elsie.nci.nih.gov/pub/iso8601.ps.gz contains this paragraph: An ordinal date is identified by a given day in a given year. A week is identified by its number in a given year. A week begins with a Monday, and the first week of a year is the one which includes the first Thursday, or equivalently the one which includes January 4. Midnight may be expressed as either 00:00:00 or 24:00:00. Peter Ilieve peter@aldie.co.uk