WEEKNUM/text/scalc/01/func_weeknum.xhpWEEKNUM function
WEEKNUM
WEEKNUM calculates the week number of the year for the internal date value as defined in ODF OpenFormula and compatible with other spreadsheet applications.Supported are two week numbering systems:
SystemDescriptionSystem 1The week containing January 1 is the first week of the year, and is numbered week 1.System 2The week containing the first Thursday of the year is the first week of the year, and is numbered week 1. That means that week number 1 of any year is the week that contains January 4th. ISO 8601 defines this system and that the week starts on Monday.
WEEKNUM(Number [; Mode])Number is the internal date number.Mode sets the start of the week and the week numbering system. This parameter is optional, if omitted the default value is 1.
SystemModeDay of the weekSystem 11Sunday2Monday11Monday12Tuesday13Wednesday14Thursday15Friday16Saturday17SundaySystem 221Monday (ISO 8601)150(ISO 8601, for interoperability with Gnumeric)
=WEEKNUM(DATE(1995;1;1);1) returns 1=WEEKNUM(DATE(1995;1;1);2) returns 1. Using System 1, the week containing January 1 is the first week of the year.=WEEKNUM(DATE(1995;1;1);21) returns 52. Week 1 starts on Monday, 1995-01-02.=WEEKNUM(DATE(1999;1;1);21) returns 53. Week 1 starts on Monday, 1999-01-04.WEEKNUM wiki page.