Recover the first Unix day's naive local ISO and bracketed timestamps through a bounded, round-trip-checked mktime fallback. Preserve successful timezone/DST conversions and omit unrepresentable timestamp prefixes rather than aborting gateway history replay.
Add regressions for parsing, rendering, replay with injection on/off, microseconds, and unsupported values. Canonical focused validation: 56 passed; original production code restored as a negative control: 21 regression failures.
476268f167