http://www08.wolframalpha.com/

learned about it from the WSJ Numbers Guy:

http://online.wsj.com/article/SB124516890985419379.html?mod=djemnumbers

simple stuff that i can easily understand gives simple results

Input interpretation:
Wednesday, January 16, 1957 to Sunday, July 19, 1959
Time span:

* More forms

2 years 6 months 3 days
Time difference from today (June 16, 2009):
52 years 5 months since January 16, 1957
49 years 10 months 28 days since July 19, 1959