Ok, here's a really basic question:

How do you compare a fund with the S&P 500? For example, I have a fund in my 401k which claims that as of August 31, it has a YTD return of 11.13%. How do you determine the S&P return for the same period?

Also, is there some way to compare other non-standard periods? For example, if I got into that fund on April 13, 2004, is there some way to compare its performance to that of the S&P?

Thanks!