I want to send a command to my program ,so an hour or a day is added to timer.
When you detect the command you can use the following:
time_t t = now();
setTime(t + X ); //X would be 3600 for 1 hour or 86400 for 1 day
OR
adjustTime(X) ; //X is + or - moves the time ahead or back X seconds ex: +3600 or -3600