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<< Click to Display Table of Contents >> ISOWEEKNUM (ISO week number) |
Syntax:
ISOWEEKNUM(Date)
Description:
This 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. On the contrary, it is based on the ISO standard 8601, which is binding in Germany, Austria and Switzerland, among other countries. It specifies the following:
1. Weeks always start on a Monday (not Sunday).
2. The first week of a year is defined as the week that includes January 4th.
Note:
This may lead to situations where December 29th, 30th and 31st are considered part of the first week of the next year – or where January 1st, 2nd and 3rd 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 it can also return the year to which the date belongs (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. The function is unknown in older versions.
See also: