# Thread: Week numbers in excel

1. I have a question. I am using the following formula to determine the week number of a date, except I need to modify it so that Friday is the first day of the week. Can I modify this formula, or do I need to try a new one?

=INT((B4-DATE(YEAR(B4-WEEKDAY(B4-1)+4),1,3)+WEEKDAY(DATE(YEAR(B4-WEEKDAY(B4-1)+4),1,3))+5)/7)

Thanks

2. [s]Your formula is calculating based on the first Monday of the year or Jan 3rd, I changed the formula to start on the first Friday of the year or Jan 1st.
Try this (the 1s used to be 3s.
:
=INT((B4-DATE(YEAR(B4-WEEKDAY(B4-1)+4),1,1)+WEEKDAY(DATE(YEAR(B4-WEEKDAY(B4-1)+4),1,1))+5)/7)[/s]

I apologize as I did not test fully.

3. This one should do it.

=INT((B4-DATEVALUE("1/1/2010"))/7)+1

4. This formula will calculate based on current year - you should not have to change it from year to year.

change the -6 to the weekday number that you want to start your week - with Sunday = 1, Monday = 2, etc

=INT((\$B2-(DATE(YEAR(\$B2),1,1) - WEEKDAY(DATE(YEAR(\$B2),1,1)-6)+7))/7)+1

5. Works perfect! Thanks for your help!

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