Finding date from weeknumber

[alhajoth]

Hi,

I need to find the date, preferably of the sunday, in a given week.
For example, I have as input week 27 2008, I'd like to find the date of the sunday in that week.

I'm actually trying to find the number of weeks between two such sets of input, for example week 27, 2008 to week 12, 2010.
I figured if I could find the dates, I could simply use

difference=int(date2-date1)/7

but if anyone has a better idea, let me know.


A

[zbor]

I think that formula will return you an mistake...

For example 19.7.1010 - 1.2.2010 will give you 2 weeks while there's 3 weeke difference...

This maybe:

=WEEKNUM(date1, 1)-WEEKNUM(date2, 1)

[zbor]

Important:

The WEEKNUM function considers the week containing January 1 to be the first week of the year. However, there is a European standard that defines the first week as the one with the majority of days (four or more) falling in the new year. This means that for years in which there are three days or less in the first week of January, the WEEKNUM function returns week numbers that are incorrect according to the European standard.

[alhajoth]

But as long as I'm consistent throughout the macro, for example by specifying that a week always begins on a monday, I should be able to work around that problem with WEEKNUM.

Still, I need to find the date first..
Any suggestions on that problem?

[zbor]

IS sunday first or last day of the week?

This maybe: ="27.12.2009"+(E3-1)*7

(where 27.12.2009 is last sunday of year before).

[alhajoth]

Sunday would be the last day of the week.
This macro must be flexible and able to work over several years, so I don't know the last sunday of the previous year.
If each year had 52 weeks, this would have been easy, but some years have 53 weeks and I don't know if there is a simple way of finding out which ones they are.