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<< Click to Display Table of Contents >> ISOWEEKNUM (ISO week number) |
Syntax:
ISOWEEKNUM(Date)
Description:
Returns the ISO week number of a date (i.e. the week number according to the ISO 8601 standard).
Unlike the WEEKNUM function, this function does not use the calculation method commonly used in the USA and many other parts of the world. Rather, it is based on the ISO standard 8601, which is binding in Germany, Austria and Switzerland, among others. It specifies the following:
1. Weeks start on Monday (not Sunday).
2. The first week of a year is defined as the week that contains January 4th.
Note:
This may lead to situations where December 29, 30 and 31 are considered part of the first week of the next year – or where January 1, 2 and 3 are considered part of the last week of the previous year. See examples below.
Tip: For this reason, PlanMaker provides an alternative (not Excel-compatible) function called ISOWEEK. This returns exactly the same results, but can optionally return the year to which the date belongs to (according to the ISO 8601 standard).
Example:
ISOWEEKNUM("01/01/2020") returns 1.
ISOWEEKNUM("01/01/2017") returns 52 (since this day was a Sunday).
Compatibility notes:
Microsoft Excel supports this function only in version 2013 or later. In older versions, the function is unknown.
See also: