calendarweek – Calculate the week number of a date

Calculates the week number of a given date; usage is \calendarweek{30}{12}{2006}. The package uses the e-TeX extensions (available in any current distribution); it is suitable for inclusion into larger calendar-based packages.

Watch out: Dec 29 can be evaluated to week 1 of the next year; and Jan 3 can be week 53 of the previous year.