Adding 1 month to February 28th results in March 28th

I actually don't know, whether this is a bug but it was not the behavior I expected so I report it.

Consider the following code:

>>> datetime.date(2014,12,31) + relativedelta(months=1) + relativedelta(months=1) + relativedelta(months=1)
datetime.date(2015, 3, 28)
>>> datetime.date(2014,12,31) + relativedelta(months=3)
datetime.date(2015, 3, 31)

I really expected both examples to result in the same date.

Or want may I do to achieve the same result (other than manually check for february 28th/29th)