int WeekNum(double d[, int n1, int n2])

The 3rd parameter int n2 decides which week is the first week of the year.

• 1 (default) - The week containing January 1 is the first week of the year.

• 2 - European week numbering system ((complies with ISO standard 8601, section 3.17)), week that has at least four days in the new year is 1st week..

E.g. January 1, 2022 is on Saturday, so WeekNum(1/2/2022, 1,1) will return 1, while WeekNum(1/2/2022, 1,2) will return 52.

Such parameter is also added to datepart() function