The ISOWEEKNUM function returns the ISO week number of a supplied date.
- This function was only introduced in Excel 2013 and so is not available in earlier versions of Excel.
|date||The date argument|
Note: It is recommended that the supplied date argument is input as either:
- A reference to a cell containing a date, or
- A date returned from a formula
Warning: If you attempt to input the date as text, there is a chance that Excel may misinterpret this due to different date systems, or date interpretation settings.
Common Function Error(s)
|Problem||What went wrong|
|#VALUE!||Occurs if the supplied date argument is a text value that can not be interpreted as a date|
|#NUM!||Occurs if the supplied date argument is a numeric value, but is not recognized as a valid date|
The ISO (International Organization for Standardization) week date system is a leap week calendar system that is part of the ISO 8601 date and time standard.
Each week of the ISO date system starts on a Monday, with week number 1 set to the first week of the year that contains a Thursday.