Epoch Time Calculator

Work with epoch time across seconds, milliseconds and different epoch bases.

About Epoch Time Calculator

Different systems count from different zero points, so converting between them is a fixed offset. Windows FILETIME and GPS time are the two most commonly encountered alternatives to Unix time. Mixing epoch bases produces errors of decades rather than hours, which makes them easy to spot but easy to introduce when integrating systems.

Formula

Epoch Time

Unix seconds = epoch seconds + the offset between the two epoch bases

epoch base: The zero point a system counts from
FILETIME: Windows counts from 1601, offset by 11,644,473,600 seconds

Worked example

With the default values below, Epoch Time Calculator returns Equivalent Unix Seconds of 1,750,000,000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Epoch secondsminimum 0 s: 1,750,000,000 s
Epoch baseone of Unix, 1 January 1970, Windows FILETIME, 1 January 1601, GPS, 6 January 1980: Unix, 1 January 1970

Results

Equivalent Unix Seconds: 1,750,000,000 s
Calendar Date in UTC: 2025-06-15
Epoch Milliseconds: 1,750,000,000,000 ms
Years Since the Unix Epoch: 55.4553 years
Offset Applied to Reach Unix Time: 0 s

Step by step

1Values used
2Epoch Time
3Equivalent Unix Seconds= 1,750,000,000 s
4Calendar Date in UTC= 2025-06-15
5Epoch Milliseconds= 1,750,000,000,000 ms
6Years Since the Unix Epoch= 55.4553 years
7Offset Applied to Reach Unix Time= 0 s

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Epoch Time calculated?

Unix seconds = epoch seconds + the offset between the two epoch bases Different systems count from different zero points, so converting between them is a fixed offset. Windows FILETIME and GPS time are the two most commonly encountered alternatives to Unix time.

Why does Epoch Time matter?

Mixing epoch bases produces errors of decades rather than hours, which makes them easy to spot but easy to introduce when integrating systems.

What values do I need to enter?

This calculator takes 2 inputs: Epoch seconds, Epoch base. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.