Pushing my four month old baby's schedule back a few hours?? help?

It will be difficult the first few nights but this is a common mistake new parents make, put him to bed between 8pm and 9pm, no exceptions. This will be an appropriate time when he is older so the habit needs to be made now. Also (proven fact) children sleep better and longer when they go to bed earlier instead of exhausted. So put him to bed and let him cry himself to sleep for as long as it takes for him to follow the routine. You will notice within a few days that he stops fighting it so much and might even sleep in until 6 or 7 am. Be consistent! As hard as it will be, he only goes by the routine you have made so just start a new, better routine cold turkey.