WEEKNUM
Syntax:
WEEKNUM ( serial-value [ , weekday-start-flag ] )
Description: Computes the week number of the date corresponding to serial-value. The week containing January 1 is the first week of the year, and is numbered week 1.
Arguments:
| Name | Type | Description | ||||||
|---|---|---|---|---|---|---|---|---|
| serial-value | number | The date whose week number is to be computed. The value of serial-value is truncated to an integer. | ||||||
| weekday-start-flag | number | When truncated to integer, indicates the weekday on which the week begins, as follows: 
 | 
Return Type and Value: number – The week number of the date corresponding to serial-value.
However, if
- serial-value is out of range for the current date base value, - #NUM!is returned.
- weekday-start-flag is out of the range specified in the table above, - #NUM!is returned.