It will pick up the metadata from the clip.
So the first thing to check is whether your clip has metadata. Click VIEW/PLAYHEAD INFO and skim your mouse over the clip. Do you see any data and time info?
You can add date and time info in iMovie by right-clicking on the Event clip and editing the date and time. i am not sure if this will populate the title, but it might. In older versions of iMovie, it would not.
A better solution (assuming you know the date and time) is to select that clip in the Event.
Then right-click on the clip and select Reveal in Finder.
In the Finder, right-click/COPY. Go to your desktop and right-click PASTE. On this copy of the clip, change the name of the clip to clip-yyyy-mm-dd hh;mm;ss;ext where hh is hours in 24 hour time, ext is the current extension, and the rest should be self explanatory.
Once you have done this, import it into iMovie using FILE/IMPORT/MOVIES...
It is OK to import it into the same Event.
Now it should have the correct date and time metadata.
