The correct formula that Wolfram should be using here is floor((cur_yr - old_yr)x365.25), assuming you are interested only in the recent past where the 365.25 holds true.

As an aside, floor(365.25x(2011-1984))+138 gives 9,999 days elapsed which would make today the 10,000th day, as stated by Zuckerberg.

EDIT: this formula only works when you begin on a day after a leap day during a leap year, thanks hennypenny