How to use waypoint start-time?

[AndrewS]

During the simulation development using AI on FlightGear, I needed to start the simulation of some cars on the ground after some time; for example, the total simulation began at 2 pm, and the vehicles started moving 5 minutes ago.

When I used the command WAIT on Flightplan:
<wpt>
<name>WAIT</name>
<time-sec>300</time-sec>
</wpt>

The cars start at the same time as the simulation, depending on how I created the simulation. Because of this, I'm interested in how I use the "start-time" properties to start the AI simulation at the time, for example, 2:05 pm, after 5 minutes.

/ai/models/groundvehicle/waypoint/start-time