Timestamp.dayofyear method returns day of month.
I noticed this while doing some work where I'm filtering values based on day of year:  The dayofyear method of the Timestamp class returns the day of the month, not the day of the year.  I realize there are a number of ways to compute this, none of which is very fast, but it could be changed to return the difference, in days, between it's own value and 0000 01 January of the current year.

In pandas/src/datetime.pyx, the problematic code is, starting on line 147/148, in the definition of the function.
