Please Note: This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here: Calculating the Last Day in a Week Number.

Calculating the Last Day in a Week Number

by Allen Wyatt
(last updated September 22, 2018)

You probably know that you can use the WEEKNUM function to return the week number in a year for a given date. What if you want to do the reverse—to determine the last day of a particular week if all you have is the week number within the year? For instance, if you were to specify week 37, you would like to figure out the date of the last day in that particular week.

There is no built-in function to figure out the desired date, but there are a number of ways that you can approach the problem and figure it out. In these examples we will assume that the year is in cell A1 and the desired week number is in cell B1.

The first approach is to calculate the first day of the desired year, add seven days for each of the weeks, and then subtract the weekday number for the first day of the year.

=DATE(A1,1,1)+B1*7-WEEKDAY(DATE(A1,1,1))

This formula returns a date that always represents the last day of the week, if the week ends on a Saturday. If you want the week to end on a different day of the week then the formula becomes more complex. If you want the week to end on a Sunday, then you simply need to add 1 to the formula:

=DATE(A1,1,1)+B1*7-WEEKDAY(DATE(A1,1,1))+1

Applying this same logic, you might think that you could figure out weeks ending on Friday by simply subtracting 1 from the formula. This is not the case since you are using the beginning of the year as your base. If you subtract 1, you run into the problem where January 1 of whatever year is a Saturday; if you subtract 1 you don't end up with the first Friday of the year but instead end up with December 31 of the previous year. To calculate for weeks ending on Friday you need a much more complex formula:

=DATE(A1,1,6-WEEKDAY(DATE(A1,1,1))+
((6-WEEKDAY(DATE(A1,1,1))<0)*7)+1)+((B1-1)*7)

Since some years have 52 weeks and some have 53—again depending on whether weeks end on Friday, Saturday, or Sunday—it is a good idea to modify the formulas so that they check to see if the date being returned is within the same year that you are analyzing. If you don't check this, then the formulas provided thus far will happily return dates for week 73, week 89, or week 123 of any given year—they simply adjust the date into the appropriate future year.

Here is the formula for weeks ending in Friday:

=IF(YEAR(DATE(A1,1,6-WEEKDAY(DATE(A1,1,1))+
((6-WEEKDAY(DATE(A1,1,1))<0)*7)+1)+((B1-1)*7))=A1,
DATE(A1,1,6-WEEKDAY(DATE(A1,1,1))+((6-WEEKDAY(DATE(
A1,1,1))<0)*7)+1)+((B1-1)*7),"")

If the date calculated is not in the same year as what is specified in cell A1, then the formula returns nothing. Here is the formula for weeks ending in Saturday:

=IF(YEAR(DATE(A1,1,1)+B1*7-WEEKDAY(DATE(A1,1,1)))=A1,
DATE(A1,1,1)+B1*7-WEEKDAY(DATE(A1,1,1)),"")

Finally, here is the formula for weeks ending in Sunday:

=IF(YEAR(DATE(A1,1,1)+B1*7-WEEKDAY(DATE(A1,1,1))+1)=A1,
DATE(A1,1,1)+B1*7-WEEKDAY(DATE(A1,1,1))+1,"")

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (6750) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Calculating the Last Day in a Week Number.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He is president of Sharon Parq Associates, a computer and publishing services company. ...

MORE FROM ALLEN

Exporting Latitude and Longitude

A handy way to store latitude and longitude values in Excel is to treat them as regular time values. When it comes around ...

Discover More

Positioning Graphics Evenly

If you need to arrange a group of graphics so that they are evenly distributed between a starting point and an ending ...

Discover More

Leaving Even Pages Blank

Want to print your document only on odd-numbered pages in a printout? There are a couple of things you can try, as ...

Discover More

Save Time and Supercharge Excel! Automate virtually any routine task and save yourself hours, days, maybe even weeks. Then, learn how to make Excel do things you thought were simply impossible! Mastering advanced Excel macros has never been easier. Check out Excel 2010 VBA and Macros today!

More ExcelTips (menu)

Calculating the Day of the Year

Need to know what day of the year a certain date is? You can figure it out easily using the formulas in this tip.

Discover More

Converting European Dates to US Dates

Those in Europe use a date format that is different than those in the US; this is not news. But what if you need to ...

Discover More

Calculating Week-Ending Dates

When working with dates, you may need to figure out all the dates on which weeks end in a given year. There are several ...

Discover More
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

View most recent newsletter.

Comments

If you would like to add an image to your comment (not an avatar, but an image to help in making the point of your comment), include the characters [{fig}] in your comment text. You’ll be prompted to upload your image when you submit the comment. Maximum image size is 6Mpixels. Images larger than 600px wide or 1000px tall will be reduced. Up to three images may be included in a comment. All images are subject to review. Commenting privileges may be curtailed if inappropriate images are posted.

What is four less than 5?

There are currently no comments for this tip. (Be the first to leave your comment—just use the simple form above!)


This Site

Got a version of Excel that uses the menu interface (Excel 97, Excel 2000, Excel 2002, or Excel 2003)? This site is for you! If you use a later version of Excel, visit our ExcelTips site focusing on the ribbon interface.

Newest Tips
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

(Your e-mail address is not shared with anyone, ever.)

View the most recent newsletter.