Returns a number that indicates where the week falls numerically within a year.
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.
If this function is not available, and returns the #NAME? error, install and load the Analysis ToolPak add-in.
- On the Tools menu, click Add-Ins.
- In the Add-Ins available list, select the Analysis ToolPak box, and then click OK.
- If necessary, follow the instructions in the setup program.
Serial_num is a date within the week. Dates should be entered by using the DATE function, or as results of other formulas or functions. For example, use DATE(2008,5,23) for the 23rd day of May, 2008. Problems can occur if dates are entered as text.
Return_type is a number that determines on which day the week begins. The default is 1.
||Week begins on Sunday. Weekdays are numbered 1 through 7.
||Week begins on Monday. Weekdays are numbered 1 through 7.
Microsoft Excel stores dates as sequential serial numbers so they can be used in calculations. By default, January 1, 1900 is serial number 1, and January 1, 2008 is serial number 39448 because it is 39,448 days after January 1, 1900. Microsoft Excel for the Macintosh uses a different date system as its default.
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
- Create a blank workbook or worksheet.
- Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
- Press CTRL+C.
- In the worksheet, select cell A1, and press CTRL+V.
- To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
|March 9, 2008
||Number of the week in the year, with a week beginning on Sunday (11)
||Number of the week in the year, with a week beginning on Monday (10)
Note March 9, 2008 is a Sunday.