Derives the numeric value for the week within the year (1, 2, etc.). Input must be the output of the DATE function or a reference to a column containing Datetime values. The output of this function increments on Sunday.

Week 1 of the year is the week that contains January 1.

NOTE: If the source Datetime value does not include a valid input for this function, a missing value is returned.

Known Issue:

The current implementation of the WEEKNUM function returns a maximum value of 52. However, in some years, such as 2020, there is a 53rd week. You can add steps similar to the following to work around this issue:

derive type: single value: dateformat(date(year(myDate), 1, 1), 'yyyy\/MM\/dd') as: 'NewYearsDayforMyYear'

derive type: single value: if(datedif(NewYearsDayforMyYear, myDate, day) > (52 * 7), 53, weeknum(myDate)) as: 'weekNumforMyDate'

The above implementation differs from other platforms, such as Microsoft Excel.

Column reference example:


Output: Returns the numeric week number values derived from the MyDate column.


ArgumentRequired?Data TypeDescription
datetime_colYdatetimeName of column whose week number values are to be computed


Name of the column whose week number value is to be computed.

Tip: You cannot insert constant Datetime values as inputs to this function. However, you can use the following: WEEKNUM(DATE(2017,12,20)) .

Required?Data TypeExample Value

Example - Day of Date functions