Convert epoch seconds or milliseconds to ISO dates and back with timezone context. Fully client-side — no account, uploads, or remote storage.
Added Apr 26, 2026
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Enter a value for direction to see your result.
Converts between Unix epoch timestamps and human-readable ISO 8601 dates. Auto-detects whether the input is in seconds, milliseconds, microseconds, or nanoseconds, and renders the result in any timezone (or local browser time).
ISO_date = epoch_unix / 1000^k + 1970-01-01T00:00:00Z
1,700,000,000 seconds since the epoch is exactly 22:13:20 UTC on 14 November 2023. Multiplied by 1000 gives 1.7e12 ms.
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Magnitude 1.7e12 → milliseconds branch. Same instant as the seconds example, just at 1000× scale.
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The Unix epoch itself: 1 January 1970 at midnight UTC.
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A Unix timestamp (or epoch time) is the number of seconds that have elapsed since 1 January 1970 at 00:00:00 UTC, ignoring leap seconds. It is the most common way to store an absolute moment in time across systems.
A timestamp in seconds for a date around 2024 has 10 digits (e.g. 1700000000). The same instant in milliseconds has 13 digits. Auto-detect uses this magnitude rule, but you can override it manually.
Timestamps are timezone-agnostic — they are just a count of seconds since the UTC epoch. The display timezone in this tool only affects the readable label; the underlying instant is the same.