Calculating Week-Ending Dates

Do you keep track of information based on week-ending dates? Many businesses do, and therefore need a quick way to calculate the week-ending dates for the complete year. The dates could be easily calculated with a macro, but you can do it just as easily with formulas.

There are two formulas you can use in order to calculate your week-ending dates. Let's assume, for the sake of this example, that your year is stored in cell A1. You could then figure out the first Saturday of the year by using this formula in cell A3:

=DATE(A1,1,1)+7-WEEKDAY(DATE(A1,1,1))

This works because the WEEKDAY function returns a value of 1 (Sunday) through 7 (Saturday) for any date. If you subtract that value from 7, then you have a value of 6 (Sunday) through 0 (Saturday). When you add that value to the DATE value for January 1 of the year, you end up with the first Saturday of the year.

If you prefer to have your weeks end on Fridays, then the formula needs to change a bit:

=DATE(A1,1,1)+7-(WEEKDAY(DATE(A1,1,1)+1))

Finally, if you prefer to have your weeks end on Sundays, then the formula needs to be like this one:

=DATE(A1,1,1)+7-WEEKDAY(DATE(A1,1,1),2)

This formula uses a parameter for the WEEKDAY function that calculates weekdays that range from 1 (Monday) through 7 (Sunday).

Once you have the first week-ending date for the year (in A3, remember?), then you can calculate the rest of the week-ending dates for the year. Place the following formula in cell A4:

=IF(YEAR(A3+7)=$A$1,A3+7,"")

This checks to see if one week past the previous date is still in the year. If it is, then the new date is returned. If it isn't, then an empty string is returned. If you copy this formula from A4 down through A55, then you will have all the desired week-ending dates for the year. With the formulas in place, simply change the year in cell A1 to see how the dates change.

The range A3:A55 provides room for 53 week-ending dates, which is possible for any given year. Because you used the IF statement in the formula in cells A4:A55, then the very last value (A55) will be blank if there were only 52 week-ending dates for the year.