In any submission details there are several data like: verdict, time it was sent & judging time.... etc.

Why not to add something like:

The time when a submission is sent during the contest time.

Like: the submission was sent after MM:SS of the beginning of the contest.

It will help us to track the time taken to solve problems during the contest!

And certainly will be helpful to track this over many contests to measure the progress of solving problems in contests!