Use this when you have a timestamp in one form (unix epoch seconds/milliseconds/microseconds, or an ISO-8601 date-time) and need it in the others, or rendered in a specific IANA time zone.

Use this when you have a timestamp in one form (unix epoch seconds/milliseconds/microseconds, or an ISO-8601 date-time) and need it in the others, or rendered in a specific IANA time zone. Auto-detects the input: a number or digit-string is an epoch classified by length (~10 digits = seconds, ~13 = milliseconds, ~16 = microseconds); anything else is parsed as ISO-8601, with a naive date-time (no Z/offset) taken as UTC. Returns unix_s, unix_ms, iso_utc, iso_tz (with numeric offset), a human string, and the weekday, all in the requested zone (default UTC), correctly handling DST transitions and pre-1970 (negative) epochs. Deterministic: same input, same output. Prefer this over doing epoch/timezone arithmetic yourself. Example: { value: 1783454640, timezone: "America/Chicago" } -> iso_utc "2026-07-07T20:04:00.000Z", human "Tuesday, July 7, 2026 at 3:04 PM CDT".