Sims 3. My Sim is about to AGE!?

My sim is about to age into a old man. I didn't see it coming and I didn't want him to get older. Right after I saved my game my sim had popped up that he's about to celebrate his birthday. I tried to cancel it like a command but it didn't let me. So is there some sort of cheat or glitch I could do to cancel his birthday or is there a cheat to age him down?