# WEEKNUM function

Returns a number that indicates where the week falls numerically within a year.

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.

## Syntax

WEEKNUM(serial_num,return_type)

Important

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 might occur if dates are entered as text.

Argument

Description

Remarks

serial_num

A date within the week.

• None.

return_type

A number that determines on which day the week begins. The default is 1.

• 1 or omitted returns numbers 1 (Sunday) through 7 (Saturday). Behaves like earlier versions of Excel.

2 returns numbers 1 (Monday) through 7 (Sunday).

## General remarks

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.

## Example

To make the following example easier to understand, you can copy the data to a blank sheet and then enter the function underneath the data. Do not select the row or column headings (1, 2, 3... A, B, C...) when you copy the sample data to a blank sheet.

 Note  March 9, 2008 is a Sunday.
 1 2
 A B Date March 9, 2008 Formula Description (Result) =WEEKNUM(A2,1) Number of the week in the year, with a week beginning on Sunday (11) =WEEKNUM(A2,2) Number of the week in the year, with a week beginning on Monday (10)
 Rate this content: