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Unix Timestamp Converter

Translate epoch timestamps and ISO dates while showing UTC and local browser time.

Seconds, Milliseconds and the 1970 Assumption
The classic failure is unit confusion: 10-digit numbers are seconds, 13-digit are milliseconds, and pasting one where the other is expected yields dates in 1970 or far beyond now. Unix timestamps also carry no timezone — they are UTC by definition, and every local time is a rendering decision. That is why "the same moment" prints different clock times in Madrid and Mexico City. Dates before 1970 are negative numbers, and far-future or pre-1970 dates in other calendar systems are where timestamp math stops being the right tool.
Seconds, Milliseconds and the Time Zone Trap
A Unix timestamp counts seconds since 1 January 1970 UTC. A ten-digit number such as 1700000000 is in seconds, while a thirteen-digit number is in milliseconds, which is what JavaScript's Date.now() returns. Mixing the two puts the date in 1970 or far in the future.
A timestamp has no time zone; only the display does. Store and transmit UTC, and convert to local time only for display. When two systems disagree by whole hours, the cause is almost always a local-time conversion applied twice or not at all, not a wrong timestamp.
How the Tool Works
  1. Paste an epoch value in seconds (e.g. 1726000000) or milliseconds (e.g. 1726000000000). The tool auto-detects the scale.
  2. The result shows both UTC and your local timezone, eliminating confusion about offsets.
  3. Alternatively, enter a date and the tool computes the matching epoch value in seconds and milliseconds.
  4. Copy either representation for use in your API tests, database queries, or scripts.
Example Input & Output
Debug an API token expiry
Input: exp claim = 1726086400 (seconds)
Output: 2024-09-11 12:26:40 UTC / 14:26:40 CEST
Converting an exp to local time instantly answers "is this token still valid right now?"
Generate a timestamp for a query
Input: 2026-09-11 12:00 local time
Output: 1786…s (seconds) / 1786…000 (ms)
Generating the epoch from a calendar date is required when constructing range queries or scheduling jobs.
Common Questions
Seconds or milliseconds — how do I know?
13-digit values are almost always milliseconds; 10-digit values are seconds. The converter detects the scale automatically from the digit count.
Why do timestamps differ from my colleague’s?
The epoch instant is identical worldwide; only the displayed local time differs by timezone. Always compare in UTC to avoid confusion.
Is there a negative timestamp?
Yes, dates before 1970 produce negative epoch values, and the converter handles them correctly.
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