Melatonin helps me sleep the first four or so hours, then Zyrtec helps with the last four. You can take the Zyrtec any time since it's a 24 hrs pill, but I try to take mine around bedtime. They don't make me groggy or anything during the day, and they even help with mosquito bites!

Edit: Also Costco sells a year's supply for the cost everyone else sells a month's worth.