Do what Hard-on said. That is a good idea.

And yes, buy a timer. I use to have to do the same thing as you. I had to juggle college and my light schedule for my plants, which was not easy. Get a digi one. I bought one at Wal-mart over a year ago now for about $20. You can set it to the time you want the lights to come on, and off. Best $20 I ever spent. Trust me, it will make life so much easier. Good luck!