@*ECHO OFF
*SETLOCAL
*UNALIAS *

:: ISOWeek.btm V-1.20 May 2005 - Michael Bednarek
:: Computes ISO 8601 Week Number (condensed code)
:: Input: A legal date (>=1980-01-01, <=2099-12-31); no check.
:: Output: yyyy*100 + ww

FUNCTION ISODOWI=`%@EVAL[(%@DOWI[%1] + 5) %% 7 + 1]`
SET ThuNow=%@MAKEDATE[%@EVAL[%@DATE[%1] + 4 - %@ISODOWI[%1]],4]
SET theYear=%@YEAR[%ThuNow]
SET ISOWeek=%@EVAL[%theYear * 100 + (%@DATE[%ThuNow] - %@EVAL[%@DATE[%theYear-01-04] + 4 - %@ISODOWI[%theYear-01-04]]) \ 7 +1]
IF %_BATCH LT 2 ECHO ISO Week: %ISOWeek
QUIT %ISOWeek