Yes. The finish is measured in milliseconds. But there are only 29.97, or maybe 59.94 frames per second in video. So getting to the correct millisecond will be impossible except with great luck.
In fact, you have probably noticed that you can see the hand about to touch, and see it touching, but not all that often will you see the exact moment it touches.
So, if you want to create a timer yourself, you can do that, and cheat by using titles to create your numbers. You can make it look like your timer is correct. But it won't be.
If you want to create 60 different titles to use to cover up the frames portion of the timecode, the first is 00, then 17, then 33, 50, 67, and keep going... As you can see when you divide 1000 by 60, the real numbers are 16.6667 and 33.33333 but that is just not worth worrying about, I suppose.
Fuzzy's suggestion to use After Effects is probably the best route, but if you do not have access to AE, then you might want to consider shooting a video of an LED timer, that displays milliseconds. Shoot that at the same Frame-Rate that you used to record the swimmers. Then, just add that Video (of the timer) to Video Track 2, Scale it, and Positon it, as needed, then apply the Crop Effect to it, so that ONLY the Timer is seen. This will be a PiP (Picture in Picture). That will get you close, per Steven's comments.
I would also think about doin a Freeze Frame on that timer's video (the PiP), if you know the results.
This is a great idea. Pip. I will give it a try.
I do have AE and will give this a try. Thanks for the tip.
With AE, I would look there first. If that does not do it for you, then shooting a timer should get what you need.
Good luck, and please let us know which method you go with.
I made it work in AE with
1. Add a Timecode effect
2. Set "Time Source = Custom"
3. Set Time units = 100
However, I'm quickly realizing I don't know AE that well to do the things I
want. How do I add this timer then to Premier? How do I do a stop and
freeze the time? I think I can change the font, but how do I do that?
The video approach was easy, but it does looked weird when I put it with
background art and need to get the lighting right.
All in all I want to thank everyone for the great tips so quickly.