Unix Timestamp ↔ Date Time

Tools and Utilities • Digital and Web Utilities

Written by STEM Calculators Team Published December 24, 2025 Updated February 24, 2026

Convert in both directions: timestamp → date-time and date-time → timestamp. Use Local vs UTC carefully, and choose seconds vs milliseconds. Click Calculate to reveal relative time and a clearer timeline with distinct NOW vs SELECTED.

Milliseconds (ms) Use UTC Ready

Unix timestamp

Tip: If you paste a 13-digit timestamp, enable Milliseconds.

Date-time

The datetime picker is local-time based. When Use UTC is ON, the calculator interprets the entered fields as UTC to compute the timestamp.

Relative time hidden

Enter a timestamp or a date-time above. Live conversion will appear here.

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How to use the Unix Timestamp ↔ Date-Time calculator

1) Choose seconds or milliseconds

Leave Milliseconds (ms) OFF for standard Unix timestamps in seconds (10 digits for modern dates).
Turn Milliseconds (ms) ON for millisecond timestamps (often 13 digits).

2) Choose Local or UTC

Local: shows and interprets the date-time using your computer’s local timezone.
UTC: shows and interprets the date-time in UTC.

3) Convert timestamp → date-time

Type a number into the Unix timestamp field.
The calculator fills the Date-time field automatically.

4) Convert date-time → timestamp

Pick a value in the Date-time field.
The calculator fills the Unix timestamp field automatically.

5) Useful buttons

Now: sets both fields to the current moment.
Copy ISO 8601: copies the ISO 8601 representation in the currently selected timezone (Local or UTC).

6) Relative time and timeline

Click Calculate to show a relative-time label (for example, “3 days ago” or “in 2 hours”) and a small timeline marker around the current time.

7) Reset

Press Reset to clear the calculator and hide the relative-time section.

Unix timestamp

Date-time

Relative time & timeline

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