Due to the long half-life of T4 (about 7 days), taking your Synthroid at different times shouldn't be a real issue. It IS best to take it at the same time every day, but this is as much to reinforce the habit of making sure you are tking it as it is for effectiveness.
As for the timing of it most doctors recommend taking it in the morning as you can see by the responses, but there are some who prefer to take it before bed. Taking it before bed has advantages, because if you do it right, you won't have eaten within two hours of taking your meds. Since it is not a good idea, metabolically speaking, to eat right before bed, it has a double advantage doing it this way. Plus, some people report sleeping better for some reason wehn they take it at night.
I am not a doctor, nor have I ever played one on TV...