ISOWEEKNUM function
ISOWEEKNUM(Date) ISOWEEKNUM(Date)
Date
Number or { Number }
The date, as a sequential serial number.
Returns
Number or { Number }
The ISO week number of the given date, from 1 through 54.
Returns the ISO week number of the given date, from 1 through 54. Weeks begin on Mondays, and week number 1 is the first week of the year that contains a Thursday.