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Excel ISOWEEKNUM Function

Excel ISOWEEKNUM function
Summary 

The Excel ISOWEEKNUM function takes a date and returns a week number (1-54) that follows ISO standards, where weeks begin on Monday and week number 1 is assigned to the first week in a year that contains a Thursday.

Purpose 
Get ISO week number for a given date
Return value 
A number between 1 and 54.
Syntax 
=ISOWEEKNUM (date)
Arguments 
  • date - A valid Excel date in serial number format.
Usage notes 

The ISOWEEKNUM function returns a week number based on ISO standards. Under this standard, weeks begin on Monday and the week number 1 is assigned to the first week in a year that contains a Thursday.

Related functions 
Excel WEEKNUM function
Excel WEEKNUM Function

The Excel WEEKNUM function takes a date and returns a week number (1-54) that corresponds to the week of year. The WEEKNUM function starts counting with the week that contains January 1. By default, weeks begin on Sunday. 

Good links 
Microsoft ISOWEEKNUM function documentation

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