@echo off
echo Waiting 30 seconds...

rem The following is needed because SET
rem treats numbers starting with 0 as
rem octal values. 
rem (thus 08 and 09 are invalid)

rem 1- Get second and add single space
rem    before.

set endTime= %time:~-5,2%

rem 2- Delete zero after space

set endTime=%endTime: 0= %

rem 3-Operate
rem
rem %% is duplicated because this is a
rem batch file. Replace with single %
rem if typing in the console.
rem Also we need spaces around numbers

set /A endTime=( %endTime% + 30 ) %% 60
echo %endTime%

rem 4-Get zero again

for /L %%a in (0;1;9) do if "%endTime%"=="%%a" set endTime=0%%a

rem 5- Finally compare with time seconds
rem until we have a match.

:repeat
if %time:~-5,2%.==%endTime%. goto :end
goto :repeat
:end