calculate the month from the year and week number in excel

Question

In Excel 2007 I have a Year number and Week number and I want to work out the Month number.

The catch is that in my case the start of every week is a monday, so some

Answer 1

The ISO Week always contain January 4th, so let's get its weekday starting with monday (obviously "year" is the cell with the year):

WEEKDAY(DATE(year;1;4))

This is the number of days we need to go back from that date to find a monday (plus one)

DATE(year;1;4)-WEEKDAY(DATE(year;1;4))+1

So now we just need to count on...

DATE(year;1;4)-WEEKDAY(DATE(year;1;4))+1+weeknumber*7