Batch Epoch Timestamp Converter

Convert lists of epoch timestamps (seconds/milliseconds) to human-readable dates and vice versa.

Tested tool guide Tested browser tools Checked August 16, 2026

What Batch Epoch Timestamp Converter does and how it behaves

Give the converter multiple Unix epoch values and it produces readable date-times for the batch; switch direction to turn multiple date-times into epoch counts. It supports second- and millisecond-scale epochs, which avoids converting records one at a time. The main source of bad results is unit scale: 1700000000 is a modern timestamp when treated as seconds, while 1700000000000 identifies that same instant only when treated as milliseconds.

How the result is produced

Epoch scale

Each numeric entry is interpreted as either seconds or milliseconds from 1970-01-01 00:00:00 UTC. Millisecond values therefore carry three more decimal places for the same instant: 1,700,000,000 seconds equals 1,700,000,000,000 milliseconds. The chosen unit applies across the batch, so a scale error can affect every converted entry.

Reverse conversion

In the reverse direction, each date-time must resolve to an instant before it can become an epoch count in the requested unit. A trailing Z or numeric UTC offset identifies the intended instant. A date without a zone does not identify one worldwide instant, and an all-numeric date such as 01/02/2026 may also have an uncertain month-day order.

Good uses

Checking a pasted column of log timestamps before correlating events with readable incident times.
Converting millisecond timestamps from a spreadsheet export into dates for manual review.
Turning a list of scheduled date-times into Unix values required by a configuration or data field.

Limits and checks

Confirm the source unit. A current seconds value interpreted as milliseconds lands in January 1970, while a current millisecond value interpreted as seconds may fall outside the usable date range.
An epoch count does not contain a display timezone. The same instant may appear with a different calendar date or hour when formatted in UTC instead of local time.
Date-only and timezone-free inputs can be ambiguous. Include an explicit time and offset when the intended instant matters, and avoid uncertain numeric month-day ordering.

Common questions

Why did my timestamps convert to dates in January 1970?

The values were probably expressed in seconds but interpreted as milliseconds. A ten-digit contemporary Unix value is commonly second-scale; treating it as milliseconds places it only a few weeks after the epoch. Check the source format and use milliseconds only when the values are scaled by 1,000.

Does an epoch timestamp include a timezone?

No. Once its unit is known, an epoch value identifies an instant rather than a local timezone. A timezone becomes relevant when that instant is displayed as a calendar date, or when a calendar date is interpreted for reverse conversion. Use UTC or an explicit numeric offset when results must be reproducible across locations.

References and verification

The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.