(I found that the calculator written by Denis Makarov did not work properly on hyperbolic functions. I found out the reason and fixed the problem. I sent my corrected script back to Denis and he is going to update his web pages.)
Two S-P seismic travel-time function are built in. Click on a button (dist or SP), type in a numerical argument, and a closing parenthesis. Click "Go" to compute the distance of an earthquake from the time difference between the P- and S-arrival times, or visa versa.
See also the stand-alone travel time calculator.
9/7/2006 and 9/17/2006