WEEKNUMReturns a number representing the week of the year where the provided date falls.
Sample Usage
WEEKNUM(DATE(1969, 7, 20), 1)
WEEKNUM(“12/09/1948”, 2)
WEEKNUM(“6/14/2002”)
Syntax
WEEKNUM(date, [type])
date – The date for which to determine the week number. Must be a reference to a cell containing a date, a function returning a date type, or a number.
type – [ OPTIONAL – default is 1 ] – A number representing the day that a week starts on as well as the system used for determining the first week of the year (1=Sunday, 2=Monday).
Notes
When inputting the date, it is best to use the DATE function, as text values may return errors.
Behind the scenes, there are two week numbering “systems” used for this function:
System 1 – The first week of the year is considered to be the week containing January 1, which is numbered week 1.
System 2 – The first week of the year is considered to be the week containing the first Thursday of the year, which is numbered as week 1. System 2 is the approach specified in ISO 8601, also known as the European system for numbering weeks.
For each type, the start day and end day of a week are defined as follows when counting week numbers:
type
Day week begins on
Day week ends on
System
1 or omitted
Sunday
Saturday
1
2
Monday
Sunday
1
11
Monday
Sunday
1
12
Tuesday
Monday
1
13
Wednesday
Tuesday
1
14
Thursday
Wednesday
1
15
Friday
Thursday
1
16
Saturday
Friday
1
17
Sunday
Saturday
1
21
Monday
Sunday
2
See Also
WEEKDAY: Returns a number representing the day of the week of the date provided.
DAYS360: Returns the difference between two days based on the 360-day year used in some financial interest calculations.
DATE: Converts a year, month, and day into a date.
DATEVALUE: Converts a provided date string in a known format to a date value.