2003 Chevy Venture Starts engine

This van I'm not drive wery offten,like six mo.battery die,I put brend new,now ewri time when I start engine,got so,so hard start,I dont know is thi starter or somthing else,oh one more think clock on radio-cd player every time when engine starts go on 12:00 PM,I reset the clock and evry other time is go again on 12:00 PM,but if I drive and make like 6-7 starts after that starts normal and clock stays as is set.

Thanks for your help