Converting a string to time - simple task but don't know how to do it!

[Richard Kessler]

I have a string returned from a database expressing the time i.e. 2002-09-14
10:30:34.  I need to compare this value to the current time to determine the
amount of time elapsed between the two. I get the current time using
time.time() but I cannot find a way to convert the string from the database
into a time value (seconds from epoch) to do the simple subraction to find
seconds elapsed.

Help please...from anyone knowing how to do this simple task.

Thanks very much in advance.

Richard