@echo off
set y=%time:~0,-9%
set x=%time:~3,-6%

:add
set /a y=%time:~0,-9%
set /a x=%time:~3,-6%

if %y%==23 (set /a y=0) else (set /a y=%y%+1)

time %y%:%x%
timeout /t 5 /nobreak>nul
goto add