Hi There,
Stimulus onset and offset times are not logged automatically on pavlovia. But can be done so using a similar method to that explained here:Save onset offset time 2020.2.10 online - #2 by Becca
Note though that this is still when your computer “thinks” the stimulus is sent - as you highlight, timing is somewhat unknown “in the wild” and we cannot say that is the actual time without an external hardware measurement. So, it is a limitation to recognise when running timing based studies online.
Hope this helps,
Becca