ISOWEEKNUM

This function calculates the number ISO week number of the year for the specified date.

Syntax

ISOWEEKNUM(date)

[Required] The date to evaluate, specified as a serial number (e.g., 37806), a string (e.g., "5/9/2015"), or a cell reference.

ISOWEEKNUM("5/9/2015") give the result 19.