Separately, I'm a little skeptical of the tzdb's endeavor of even thinking about pre-Unix-epoch stuff. The bug-to-utility ratio of that stuff doesn't seem to be there. `zic` is where most of the ugly gnarliness of tzdb lies, and I sometimes feel that it would have been better if `zic` weren't an artifact others could depend on.
There are plenty of people alive today with negative birth timestamps, with many services wanting to calculate the proper local day and time each year to send them annoying pseudo-personalized birthday messages.
Or, for something a bit more agreeable: genealogy (esp. the bioinformatics queries in genetic genealogy) needs a good, high-resolution timeline to normalize events onto. Actually, the non-genetic kind of geneaology, solves a lot of vagueries in lineage as constraint-based puzzles over (local!) dates, with razor-thin margins that would be messed up without correct timezone-based calendar conversion — constraints like "two people couldn't have been related as mother and child, if the mother died at least two days before the child was born."
Separately, I'm a little skeptical of the tzdb's endeavor of even thinking about pre-Unix-epoch stuff. The bug-to-utility ratio of that stuff doesn't seem to be there. `zic` is where most of the ugly gnarliness of tzdb lies, and I sometimes feel that it would have been better if `zic` weren't an artifact others could depend on.