Calculate the numbers of months with a given day.

#include <Date.au3>

Local $iDaysToCalculate = 100

; Convert day to date
Local $iYear, $iMonth, $iDay
_DayValueToDate(_DateToDayValue(@YEAR, 1, 1) + $iDaysToCalculate, $iYear, $iMonth, $iDay)
ConsoleWrite($iYear & "/" & $iMonth & "/" & $iDay & @CRLF)

; Get the months
Local $iCalculatedMonth = _DateDiff("M", @YEAR & "/01/01", $iYear & "/" & $iMonth & "/" & $iDay)
ConsoleWrite($iCalculatedMonth & " months." & @CRLF)