ByteScope

Timestamp Converter

Unix time ↔ human time, with the timezones you care about side by side.

Your files never leave your browser — all processing is local.

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About this tool

Paste any Unix timestamp and this converter figures out the precision from its digit count — 10 digits are seconds, 13 milliseconds, 16 microseconds, 19 nanoseconds — and warns you when the result lands in an implausible year, which is the classic symptom of a precision mix-up. The output shows every format you'd reach for at once: ISO 8601, RFC 2822, your locale's format and a relative time ("3 days ago"), each with one-click copy.

The core feature is the timezone board: add as many IANA timezones as you need and read the same instant across all of them side by side — UTC next to Taipei next to your customer's timezone is the everyday reality of debugging distributed logs. Each row shows the current UTC offset and flags whether daylight saving is in effect, since DST transitions are where timestamp bugs hide. Your timezone set is remembered locally, and a live "now" readout with one-click copy covers the most common visit of all.

Everything runs in your browser using the built-in Intl API — no server, no account. The reverse direction (date picker + timezone → timestamp in seconds and milliseconds), a batch mode that converts a pasted column of log timestamps into a table with CSV export, and an input history (stored only in your browser, with one-click re-run and clear) round it out.

Frequently asked questions

How does it know if my timestamp is seconds or milliseconds?
By digit count: 10 digits ≈ seconds, 13 ≈ milliseconds, 16 ≈ microseconds, 19 ≈ nanoseconds. If the converted date falls outside a plausible range (roughly 1970–2100), the tool warns you and lets you override the precision manually — a 10-digit number interpreted as milliseconds lands in 1970, which is how those bugs usually look.
Why do my timestamp and my colleague's differ by exactly one hour?
Almost always daylight saving time or a timezone-offset assumption. Unix timestamps themselves have no timezone — they count seconds since 1970-01-01 UTC — so the difference appears when converting to local time. The timezone board shows each zone's current offset and DST status so you can spot exactly where the hour went.
Is my input history uploaded anywhere?
No. History lives only in your browser's localStorage — each entry is just the number you converted and when. You can delete single entries or clear everything, and nothing syncs or leaves your device.
Can I convert a whole column of timestamps from a log file?
Yes — batch mode accepts one timestamp per line (mixed precisions are fine, each line is auto-detected), converts them all into a table in your chosen timezone, and exports the result as CSV.
What's the maximum date it supports?
JavaScript dates cover ±8.64e15 ms from the epoch — roughly the years 271821 BCE to 275760 CE — far beyond any realistic timestamp. The famous 2038 problem affects 32-bit Unix systems, not this converter.