Documentation/Calc Functions/WEEKNUM EXCEL2003
Date and Time
Determines the week number for a date specified either by a date-time serial number or in a text string. It is assumed that January 1 always lies within week 1. You can select whether the first day of a new week is on Sunday or Monday.
WEEKNUM_EXCEL2003 exists only for interoperability with legacy documents created with older versions of Microsoft Excel. In Calc, if you open an Excel 2003 (.xls) file that contains calls to the WEEKNUM function, those calls are converted to calls to the WEEKNUM_EXCEL2003 function. If you save a document from Calc in ODS (Open Document Format for Office Applications) or OOXML (Office Open XML) format, any calls to the WEEKNUM_EXCEL2003 function are converted to refer to the WEEKNUM function.
Because of the limited applicability of this function, fuller details are intentionally omitted from this wiki.
Related LibreOffice functions:
Equivalent Excel functions: