Many of my old VCRs used a counter number which I believe was related to the number of revolutions of the recorded spindle. For example, a counter of 1560 was about 1 hour into a tape recorded in EP mode. My newer VCRs use elapsed time. I want to transfer my old tapes, but my index cards are based on the counter number, not elapsed time, so trying to find a specific clip could be tedious. I'm not sure if the counter number was standard adopted by all manufacturers at the time, but I am hoping that there is a formula to convert the counter number to elapsed time based on the recording mode.

I do remember that the counter was not linear. Two hours of EP recording was less than two times 1560, so I do not believe that it was related to the tape footage.

My Panasonic VCR from 1983 was like this. I too, had times by its counter. I'm not sure if there was a universal system back then. I've not seen such a counter in 10 years.

What you can do is find a tape, and make your own conversion chart. Find the end of a show, and then compare the time against what's in your book.

Other than that, I'd just be searching google. But it'll probably be quicker just to make your own.