Newbie:number of hits per day query

[Graham Anderson]

how do I get the average number of hits per day

I have a table like:
DateTime 		id 	ip
20050506190723	1	121.198.262

what I have so far
SELECT DateTime  , count( * )
FROM userLog
GROUP BY DateTime
LIMIT 0 , 30


I assume that DateTime would have to be converted to a specific day 
like 2005-3-7
and somehow I would need to average them

can a kind soul point me in the right direction

g