I mean, the reaper probably just counts the same as everyone else right?
It's not like he's using some different format of time just because he's a metaphysical being. Actually now that I think about it, being just bones, maybe that suggests no brain, and no decay, hence no biological clock, and a degree of immortality...
...so would such a being experience time at all, or just show up, like some sort of God that can only see death events, popping between them like we would flick through a record book. The pages and dates coming into vision and disappearing as easy as the flick of a wrist.