The ISOWEEKNUM function is one of the date and time functions. It used to return number of the ISO week number of the year for a given date. Returns a number between 1 and 54.
Syntax
ISOWEEKNUM(date)
The ISOWEEKNUM function has the following argument:
Argument
Description
date
A date you want to find the ISO week number of. Can be a reference to a cell containing a date or a date returned by the DATE function or other date and time function.