How exactly is time to climb measured?

[Solareagle]

I tried asking this on another forum and didn't get the answer I was looking for. I was mainly given a bunch of info on GA climb rates, but thats not what I'm after. What I would like to know, and speaking specifically in the context of comparing one aircrafts performance to another, how is a time to climb test peformed?

Specifically the Rare Bear Reno racer holds the piston engine record for the 3000 meter time to climb, at 91 seconds, and I'm interested in comparing some aircraft to that number, though I am unsure of how to begin the test. The test obviously ends when the plane reaches 3000 meters, but how does it begin?

Does the clock start, for example, from a dead stop when the breaks are released, or does the clock perhaps start when the aircraft is already airborne and traveling a given speed? If nobody can speak to the specifics of the world record type test I'd like to know what the ussual practice is for aquiring military time to climb numbers.

Thanks

[oakfloor]

IIRC, its from a standing start.