using rtc on mitsubishi unit

i still not sure on how to if possable use the rtc to start an output
e.g. at 4:30pm every day i want plc to switch a light on if anyone could explain how its done with small e.g. ladder diagram i would be very greatfull

Depends! What model plc are you using, A,F,FX etc.?
Tim

Yeah, it depends on which model. Most of the lower one dont have an RTC (But you can buy an add on)

The real time is held in certain registers (different models - different registers) You will have to compare the values in these registers to the actual time you want the event to happen.