Hi guys I am making a small project that involves the switching on and off of a LED lamp, all controlled with arduino. I'm failing to understand how to set the timer in coding. 
Using a rtc.
thanks 
Show us what code you have.
See these links for RTC 1307:
http://www.pjrc.com/teensy/td_libs_TimeAlarms.html
http://playground.arduino.cc/Code/time
thanks your links are very usefull ... now i try to coding and then i'll show it ... i'm novice so i'm not very expert with code ..