:: GROUNDHOG.BAT
::   Groundhog	
:: 
::      By Wronski
::        (with some recycling from stuff in
::             www.chebucto.ns.ca/~ak621/dos/bat.adv.htm 
::         and Yesterday.bat  by Rob van der Woude
::             http://www.robvanderwoude.com)
::
:: USAGE: groundhog [file] [date]  will run [file] set at date [date]
:: Default values will be used if no [file] or [date] given

@echo off
SETLOCAL

::dafault file
set file=C:\wherever\whatever.exe   
::default date
set Fakedate=09/07/2003

if %1a==a goto default
set file=%1
if %2a==a goto default
set Fakedate=%2     

:default

SET today=%date:~4,10%
date=%Fakedate%

CALL %file%

:daycount
If NOT "%date:~4,10%"=="%Fakedate%" (
SET vardate = %Fakedate%
CALL :addday
SET Fakedate=%NextDate%
SET vardate = %today%
CALL :addday
SET today=%NextDate%
goto daycount
)

date=%today% 	 ::restore previous date
ENDLOCAL
GOTO:EOF

:: * * * * * * * *  Subroutines  * * * * * * * *

:addday

:: Parse the day

SET Day=%date:~7,2%
SET Month=%date:~4,2%
SET Year=%date:~10,4%

SET NexTD=
SET NextM=
SET NextY=

:: Strip leading zeros
SET DayS=%Day%
IF %Day:~0,1%==0 SET DayS=%Day:~1%
SET MonthS=%Month%
IF %Month:~0,1%==0 SET MonthS=%Month:~1%

:: Calculate next day's date

SET /A NextD=%DayS% + 1
SET NextM=%MonthS%
SET NextY=%Year%

IF %DayS% EQU 31 (
	SET NextD=1
	Call :ChangeYear
)

IF %DayS% EQU 30 (
	SET NextY=%Year%
	CALL :ChangeMonth
) 

IF "%MonthS%/%DayS%"=="2/28" CALL :LeapYear

:: Add leading zeros to NextD and NextM if necessary
IF %NextD% LSS 10 SET NextD=0%NextD%
IF %NextM% LSS 10 SET NextM=0%NextM%

:: Nextday's date in MM/DD/YYYY format
SET NextDate=%NextM%/%NextD%/%NextY%

GOTO:EOF

:ChangeYear

IF %MonthS% EQU 12 (
	SET NextM=1
	SET /A NextY=%Year% + 1
) 
ELSE (SET /A NextM=%MonthS%+1)      
)
GOTO:EOF

:ChangeMonth

IF %MonthS%==1 (
	SET NextD=31
	SET NextM=1
	SET /A NextY = %Year%
)

IF %MonthS%==3 (
	SET NextD=31
	SET NextM=03
	CALL :LeapYear
)
IF %MonthS%==4 (
	SET NextD=1
	SET NextM=05
)
IF %MonthS%==5 (
	SET NextD=31
	SET NextM=05
)
IF %MonthS%==6 (
	SET NextD=1
	SET NextM=07
)
IF %MonthS%==7 (
	SET NextD=31
	SET NextM=07
)
IF %MonthS%==8 (
	SET NextD=31
	SET NextM=08
)
IF %MonthS%==9 (
	SET NextD=1
	SET NextM=10
)
IF %Month%==10 (
	SET NextD=31
	SET NextM=10
)
IF %Month%==11 (
	SET NextD=1
	SET NextM=12
)
IF %Month%==12 (
	SET NextD=31
	SET NextM=12
)
GOTO:EOF

:LeapYear

echo leap
:: If the year divisable by 4 then it is a leap year . . .
SET /A LeapYear = %Year% / 4
SET /A LeapYear = %LeapYear% * 4
IF NOT %LeapYear% EQU %Year% (
	SET NextD=1
	SET NextM=3
)
:: . . . unless it is also divisible by 100 . . .
SET /A LeapYear = %Year% / 100
SET /A LeapYear = %LeapYear% * 100
IF %LeapYear% EQU %Year% (
	SET NextD=1
	SET NextM=3
)
:: . . . but when it is divisible by 400 it is a leap year again 
SET /A LeapYear = %Year% / 400
SET /A LeapYear = %LeapYear% * 400
IF %LeapYear% EQU %Year% (
	SET NextD=29
	SET NextM=2
)
GOTO:EOF