parseInteger(formatDateTime($NewWeek/StartDate, ww))  with startdate 25th of december results in an non existing weeknumber.

When i use parseInteger(formatDateTime($NewWeek/StartDate, 'ww'))  with the start date of 25th of december 2017 i get '53' as a return value. But week 53 does not exist in 2017. Does anyone know what could be the issue here? It's not localize on the date time. 
1 answers

Hi Rik,

Check Erwin's answer here:

It has to do with the fact that week 1 is determined differently in Europe and the U.S.