Unix timestamps count time from 1970-01-01 UTC. Systems commonly store them in seconds or milliseconds; confusing the two can produce dates far in the past or future. The displayed local time also depends on the selected timezone.
Check the unit and timezone
Before converting a number, check the source system's documentation or the number of digits as a clue. Treat digit count as a hint, not proof.
- Paste the timestamp value.
- Select seconds or milliseconds to match its source.
- Choose UTC or the timezone relevant to the event.
- Compare the result with a known event time for plausibility.
Keep in mind: Store timestamps with an explicit timezone convention in logs and APIs to avoid ambiguity.