Does SQLite handle negative Unix time?
Yes, within limits.
For SQLite versions before 3.16.0 (2017-01-02), the "unixepoch" modifier only works for dates between 0000-01-01 00:00:00 and 5352-11-01 10:52:47 (unix times of -62167219200 through 106751991167).
Yes.
sqlite> select date('1308118481', 'unixepoch');2011-06-15
sqlite> select date('-1308118481', 'unixepoch');1928-07-19