# Function Reference

# _WeekNumberISO

Calculate the weeknumber of a given date

#include <Date.au3>
_WeekNumberISO ( [$iYear = @YEAR [, $iMonth = @MON [, $iDay = @MDAY]]] )

## Parameters

$iYear | [optional] Year value (default = current year)
$iMonth | [optional] Month value (default = current month)
$iDay | [optional] Day value (default = current day)

## Return Value

Success: | a week number of given date.
Failure: | 0 and sets the @error flag to non-zero.
@error: | 1 - faulty parameters values 99 - On non-acceptable weekstart value

## Example

    #include <Date.au3>
    #include <MsgBoxConstants.au3>

    MsgBox($MB_SYSTEMMODAL, "Todays weeknumber", "Todays weeknumber is " & _WeekNumberISO())