Hello,
corresponding to the documentation of the setDay() function, this could be a way:
setDay (date; number/name of the day in english)
Returns a new date with the day specified in parameters. It can be used to set the day of the week, with Sunday as 1 and Saturday as 7. If the given value is from 1 to 7, the resulting date will be within the current (Sunday-to-Saturday) week. If a number is given outside of the range, it will return the day from the previous or subsequent week(s), accordingly.
Regards
Lars