When does a timeout start?

[AK ref SE]

I will make sure the majority of the players of both teams are in close proximity to their bench. I will point to the timer to start clock. Why short change them! Sometimes we or I Should say "I" need the timeout so I can gather my thoughts and rest!

I have been places where they want to start the time, as soon as the whislte is blown. The warning signal for the 30 second timeout is almost going off as you are reporting the timeout to the bench.

AK ref SE