Sweetie, you need a 5 dollar timer like smokesalot suggested. If you plan on doing this for a while - You will probablyhaveto get one sooner or later. Also, check to see if the timer can handle the wattage load - too much power can start a fire!
One tip: Make sure you check to see if they go off and on at the right time. You want to keep it on a regular schedule otherwise you get some hermies!