Beetle-Racing: When does timing actually start?

(( This is kinda related to https://en-forum.guildwars2.com/discussion/comment/772891 ))

I was wondering: when does the timer actually start when you're doing a beetle-race?

IMHO it would be "logical" if the timer would start when you trigger the first checkpoint but I think it starts when you click on "Play" - which doesn't make any sense at all.

I wrote a little tool that grabs the player-position using the MumbleLink and starts/stops a timer when i'm roughly at the position of the first/last checkpoint. And that timer is always off by a couple of seconds.

If the timer actually starts when you hit "Play" that would mean that there are two different ways of taking time (during races and during time-trials).

It seems most logical to me start when you hit play. Same as adventures which use the same UI