Especially when working with calendars and dates, you might want to use the numbers of weeks. In this article, we will take a look at the WEEKNUM formula and how to use it when you create timelines, schedules or calendars. 

How to get the week number with the WEEKNUM formula

The WEEKNUM formula has 2 parts (the numbers are corresponding to the picture above):

• The date you’d like to get the week number from. 
• The system: 1 refers to a system, in which the week containing the 1st of January is week number 1. 2 describes a system in which the week containing the first Thursday of the year is week 1. The second system is known as the European week numbering system.

The picture above shows a simple example: We want to display the number of the week in a schedule. Therefore, cell E5 has this formula:

=WEEKNUM(E4,1)

The cell E4 has as the first part of the WEEKNUM formula the date we want to get the number from. The second part determines the system, in this case the week starts on Sunday. The return value in this example (screenshot taken in 2015) is 23. So the 4th of June 2015 was in week 23.