When something is happening to us, either good and exhilarating or bad and tragic, we don’t usually take notice of the exact time it happened for understandable reasons. We might want to know that in the future: when exactly did he ask my hand in marriage, when did I saw the man hit the tree etc.
Many nowadays have smartphones on them most of the time. Smartphones can record many useful things: sudden movements, sounds, vibrations, and maybe even heartbeats. These can help pinpointing the exact time something surprising happened.