How to Compute ISO Week Numbers Correctly in Alteryx?

Hello Alteryx Community,

I'm currently working on a project where I need to calculate the ISO week number for a given date in Alteryx. The ISO week number system starts with Monday as the first day of the week. Below is an example of dates with Numweek. For 6/26/2025, numweek is 26. I tried looking for a formula but was not able to find one.

I'm looking for guidance on how to accurately compute the ISO week number in Alteryx. Any insights, formulas, or best practices would be greatly appreciated!

Thank you in advance for your help!

Kamen

Workflow

Date Time

Accepted answers

davidskaife

Hi @KamenRider

Not sure if the simple datetimeformat to Weeknum and add 1 to it will work for all dates, i suspect not, but that works for your examples.

Screenshot 2025-07-04 140131.png

Another way is using this formula

PadLeft(ToString(FLOOR(DateTimeDiff(DateTimeAdd([DateTime_Out],4-Switch(DateTimeFormat([DateTime_Out],"%a"),7,"Mon",1,"Tue",2,"Wed",3,"Thu",4,"Fri",5,"Sat",6),"days"),DateTimeParse(ToString(ToNumber(DateTimeFormat(DateTimeAdd([DateTime_Out],4-Switch(DateTimeFormat([DateTime_Out],"%a"),7,"Mon",1,"Tue",2,"Wed",3,"Thu",4,"Fri",5,"Sat",6),"days"),"%Y")))+'-01-01',"%Y-%m-%d"),"days")/7)+1),2,"0")

Workflow with both examples attached

ISO Week Number.yxmd

All comments

davidskaife

Hi @KamenRider

Not sure if the simple datetimeformat to Weeknum and add 1 to it will work for all dates, i suspect not, but that works for your examples.

Screenshot 2025-07-04 140131.png

Another way is using this formula

PadLeft(ToString(FLOOR(DateTimeDiff(DateTimeAdd([DateTime_Out],4-Switch(DateTimeFormat([DateTime_Out],"%a"),7,"Mon",1,"Tue",2,"Wed",3,"Thu",4,"Fri",5,"Sat",6),"days"),DateTimeParse(ToString(ToNumber(DateTimeFormat(DateTimeAdd([DateTime_Out],4-Switch(DateTimeFormat([DateTime_Out],"%a"),7,"Mon",1,"Tue",2,"Wed",3,"Thu",4,"Fri",5,"Sat",6),"days"),"%Y")))+'-01-01',"%Y-%m-%d"),"days")/7)+1),2,"0")