### ISOWEEKNUM(date)

Returns the number of the ISO week of the year for a given date.

 date The date.

#### Remarks

 * Added in Excel 2013.* This function returns a number between 1 and 54.* The week number returned is according to the European ISO standard. All weeks start on a Monday and week number 1 is assigned to the first week that contains a Thursday.* If "date" is not a valid date, then #VALUE is returned.* If "date" is not a valid number, then #NUM is returned.* You can use the NOW function to return the serial number of the current system date and time.* You can use the TODAY function to return the serial number of the current system date.* You can use the WEEKNUM function to return the week number in the year for a given date.* For the Microsoft documentation refer to support.microsoft.com

 A 1 =TODAY() = Wednesday, September 01, 2021 2 =NOW() = Wednesday, September 01, 2021, 12:56 3 =ISOWEEKNUM(A1) = 35 4 =ISOWEEKNUM(A1+7) = 36 5 =ISOWEEKNUM(A2+14) = 37 6 =WEEKNUM(A1,21) = 35

 1 - What is the current system date. This cell has been formatted with the number format "dddd, mmmm dd, yyyy".2 - What is the current system date and time. This cell has been formatted with the number format "dddd, mmmm dd, yyyy, hh:mm".