30 days hath September

Why does February have 28 days? Is it our token "lunar month"? Wouldn't it make more sense if it had 29 days and take a day away from one of the 31-day months? There are seven 31 day months, four 30 day months, and one 28 day month. Wouldn't it be much easier for people if there were six 31 day months and six "non-31-day" months, and they alternated? Or do seven 30 day months and five 31 day months (and once every 4 years have six 31 day months)?

[Note to Sara who probably doesn't read this: Rabbit, Rabbit, Rabbit]