Returns 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 is1] - 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.