It would be interesting to see this update in realtime. You see someone about to get in their car, with a death time 5 mins from now. You call out "hey", they stop, see you were talking to someone else. The date updates to 30 years in the future, as that momentary pause meant they won't be in the place they would have when someone runs a red light.
Somewhere unseen, someone's number changes from 20 years away to 5 mins away.
It kind of ruins the concept if you can't use the information to change the outcome. Or maybe just makes it sad, every time you try to save someone they die at that time anyway. Then over time you work out that the clock knew what actions you were going to do, and by trying to interfere with the people with short times you actually caused their deaths.