1988 to 2013 is 25 years, so 365 * 25.
1992, 1996, 2000, 2004, 2008, 2012 were leap years, so +6
Note: Leap year every 4 years, skip it every 100 years, throw it back in every 400 years. 2000 was a leap year.
December 2 to January 1 is 30 days, so +30
January has 31 days, February has 28 days (in 2014), March has 31 days, April has 30 days, so +120.
May 1 to May 10 is 9 days, so +9
365 * 25 + 6 + 30 + 120 + 9
9125 + 165
9290 days.
Or go here: http://www.timeanddate.com/date/duration.html