WEEKNUM

The WEEKNUM function returns the number of the week within the year for a given date/time value or date string.

WEEKNUM(date, first-day)

date: A date/time value or date string.

first-day: An optional modal value that specifies whether weeks should begin on Sunday or Monday.

Sunday is 1 (1 or omitted): Sunday is the first day (day 1) of the week and Saturday is day 7.

Monday is 1 (2): Monday is the first day (day 1) of the week and Sunday is day 7.

Example

=WEEKNUM(“7/12/2009”,1) returns 29, if Sunday is considered the first day of the week.

=WEEKNUM(“7/12/2009”,2) returns 28, if Monday is considered.