I thought I should put this in as a guide.

Notes:

• The keyboard shortcut shown should work with any QWERTY keyboard.
• With every video, be sure that you count how many frames are in a second. Some submissions have had FPS that are not multiples of 30.
• Don't forget to add a frame at the end.
• It should take less than 2 minutes to time any run using this method.

Sample calculation:

https://www.speedrun.com/run/y45gn8dm

Start frame: 1 minute, 58 seconds, 8 frames End frame: 2 minutes, 1 second, 5 frames Total time: (2*60 + 1 + (5+1)/30) - (60 + 58 + 8/30) = 2.933 seconds