@ECHO OFF
*SETLOCAL
:: Age.BTM Calculate age in years, months, days
:: Author: Michael Bednarek (mb AT mbednarek.com)
:: Input:  d1 m1 y1 d2 m2 y2
:: Output: Age in yyyy mm dd
:: Source: http://stackoverflow.com/questions/453208/how-can-i-calculate-the-age-of-a-person-in-year-month-days
::         (replaced FLOOR() with INT() to allow for 4DOS)
:: Needs JULIAN.BTM as a workaround to compute something similar to the Unix "epoch"

FUNCTION tm=`%@EXEC[@CALL JULIAN.BTM %1 %2 %3] %JULIAN`

SET d1=%1
SET m1=%2
SET y1=%3
SET d2=%4
SET m2=%5
SET y2=%6

SET t1=%@EVAL[%y1 * 12 + %m1 - 1]
SET t2=%@EVAL[%y2 * 12 + %m2 - 1]
SET dm=%@EVAL[%t2 - %t1]
IFF %d2 GE %d1 THEN
  SET r=%@INT[%@EVAL[%dm / 12]] years, %@EVAL[%dm %% 12] months, %@EVAL[%d2 - %d1] days
ELSE
  SET dm=%@EVAL[%dm - 1]
  SET t2=%@EVAL[%t2 - 1]
  SET r=%@INT[%@EVAL[%dm / 12]] years, %@EVAL[%dm %% 12] months, %@EVAL[%@tm[%d2 %m2 %y2] - %@tm[%d1 %@EVAL[%t2 %% 12 + 1] %@INT[%@EVAL[%t2 / 12]]]] days
ENDIFF
ECHO %r
UNSET d1 m1 y1 d2 m2 y2 r