Right time to take allergy meds

Patient: I take Zyrtec 10 mg daily. I need to know what time to take this so I can get up at 2 a.m. or so to work. I’ve been taking it about noon, but that isn’t working and I’ve tried various other times during the day, but I can’t seem to find the right time. I most always take a nap in the afternoon about 3 p.m. or so; if I don’t, I find it hard to fall asleep at night.