Every once in a while I come across a situation where I would like to set the start time, or measure, to some point after the very beginning of the time line - kinda like a "count-in" time. What I mean is that, instead of starting at measure 1, for example, the time line might begin at, say, -2, then count down to -1, and then the song would begin at measure 1. Similarly, if the time ruler was set to seconds, the start time might be -2 sec, then count up to -1, 0 (the beginning of the song), 1, 2, ...
Why? Well, if I'm working with a midi representation of a piece of printed music, it's easier to find or enter a given measure if the ruler matches what's on the page. Usually, there's an offset of a couple of measures in the DAW to allow for some pre-start automation. Of course, it's not that hard to add or subtract to figure that out, so this is not exactly a showstopper, but it might be useful. It also might be helpful to have that "zero point" freely movable to allow quick calculations of time or measure durations of sections of the song starting in the middle of the song.
... 'just a thought.