# Using the WEEKNUM Function

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: Using the WEEKNUM Function.

One of the functions provided in the Analysis ToolPak is WEEKNUM. This function is used, oddly enough, to return the week number represented by a particular date. You use the function in this way:

```=WEEKNUM(A5,1)
```

In this instance, A5 contains a date serial number, and the value 1 indicates that WEEKNUM should assume that all weeks start on a Sunday. If you prefer your weeks to begin on Mondays, then you can use the value 2 instead.

You should realize that WEEKNUM always considers the first day of any given year to be in the first week of the year. Thus, it is possible for the above formula to return up to 54 weeks in a year. How can this be? Let's use the year 2011 as an example. In 2011 January 1 falls on a Saturday. As far as WEEKNUM is concerned, this is in the first week of the year. Now, January 2 for that year falls on a Sunday. Since WEEKNUM believes that every Sunday starts a new week, the second day of the week is considered in the second week of the year.

This is fine, until you get to the end of the year. The fifty-second week of 2011 ends (according to WEEKNUM) on December 24, and the fifty-third week begins on December 25 (a Sunday).

An even more interesting scenario is when the year begins on a Saturday and the year is a leap year. This happened in the year 2000. In that instance, the fifty-third week began on December 24, and the fifty-fourth week began on December 31.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2326) 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: Using the WEEKNUM Function.

Related Tips:

Program Successfully in Excel! John Walkenbach's name is synonymous with excellence in deciphering complex technical topics. With this comprehensive guide, "Mr. Spreadsheet" shows how to maximize your Excel experience using professional spreadsheet application development tips from his own personal bookshelf. Check out Excel 2013 Power Programming with VBA today!

 *Name: Email: Notify me about new comments ONLY FOR THIS TIP Notify me about new comments ANYWHERE ON THIS SITE Hide my email address *Text: *What is 5+3 (To prevent automated submissions and spam.)

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

# Our Company

Sharon Parq Associates, Inc.

# Our Sites

Tips.Net

Beauty and Style

Cars

Cleaning

Cooking

ExcelTips (Excel 97–2003)

ExcelTips (Excel 2007–2016)

Gardening

Health

Home Improvement

Money and Finances

Organizing

Pests and Bugs

Pets and Animals

WindowsTips (Microsoft Windows)

WordTips (Word 97–2003)

WordTips (Word 2007–2016)

Excel Products

Word Products

# Our Authors

Author Index

Write for Tips.Net