When I set simulations(tried smoke, rigid body, hair dynamics, and cloth so far) to start at negative frames, I always get this message above the bake buttons:
There's also a gap in the bar on the timeline at frame 0, which I assume is the cause of it:
Would it be better to start simulations on frame 1 and offset the rest of the keyframes instead? Or is there a way to get blender to bake frame 0? Or should I just ignore that message?