Time.diff gives wrong answer for February in leap years

> Time.diff(Time.new(2012, 03, 01), Time.new(2012, 02, 01))
>  => {:year=>0, :month=>0, :week=>4, :day=>1, :hour=>0, :minute=>0, :second=>0, :diff=>"4 weeks, 1 day and 00:00:00"} 

So it shows the time diff as 4 weeks and 1 days between February and March, but this should be returning 1 month.
