Could be over-stimulated. Maybe when you get home try to get him ready for bed by lowering or using a soft night light instead of bright lights, turn off any sounds from tv or radio. Try not to talk or interact with him much as this will stimulate him more. The quietness and dim lights help wind them down.
Or what a lot of my friends do - they simply dont't go out close to baby's sleep time. I dont't find it practical all the time but I guess it helps if you really want bub to sleep especially in the early months