About the timestamp converter
Unix time and time zones
Unix timestamps count seconds or milliseconds since 1970-01-01 UTC. Converting to human-readable dates requires knowing whether your source is in seconds or milliseconds and which time zone should display for humans.
Always store absolute instants in UTC at the boundary of your system and convert to local zones at presentation time when possible.
Common debugging scenarios
Off-by-one thousand errors happen when APIs mix seconds and milliseconds. If a date looks decades wrong, check the unit first before chasing logic bugs.
Daylight saving transitions create duplicate or skipped local clock times; represent recurring events with explicit rules rather than naive offsets.
Interoperability
ISO8601 strings include offsets that make intent clearer than bare integers. Prefer them in new JSON APIs while documenting legacy integer fields until clients migrate.
Log correlation benefits from consistent precision: pick millisecond or microsecond resolution team-wide for trace IDs tied to timestamps.