hi hoon
u may hv to adjust whole day's schedule so that he sleeps at a reasonable time at night.
i think he sleeps too much during the day.
try to limit nap to max 2-3 hours for entire day.
e.g. ideal nap times
9 - 10.30am
2.30 - 3.30pm
working towards the targetted nap time takes slow adjustment. slowly shorten naps, cut 15min every few days. when it's time to wake him up, turn on lights, make noise, read book loudly, play with the toys etc. make sounds of things that he likes to do, so that he will wake up "happily" & ready to play.
if u find that he is settling into nap times different fm the above, that's fine, follow his bio-clock, most impt is not too have too many hrs of daytime nap.
by 8+pm or even 7+ he should be tired, give milk n zzz n hopefully he will sleep through...
but i wonder what is milk schedule like after 8+? any night feeds? cos when u fiddle with day schedule, sometimes night schedule will inevitably change too!