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Get number of milliseconds since Unix epoch

I'm having fun creating a small open-source project(more about that later). In a part of this project I need to integrate with an existing API.

Here is (part of) the JSON schema that describes the data contract:

As you can see I need to specify a timestamp value which should be provided as a number. The description adds some extra details:

A number representing the milliseconds elapsed since the UNIX epoch.

Mmmh. The question is first of all what is the UNIX epoch and second how can I generate this number in C#?

Let’s find out!

The UNIX epoch

The Unix epoch is the time 00:00:00 UTC on 1st January 1970. Why this date? No clue, it seems to be just an arbitrary date. It is used to calculate the Unix time.

If you want to learn more, check out Wikipedia.

Get number of milliseconds since Unix epoch in C#

Now that we now what the UNIX epoch is, what is the best way to calculate the number of milliseconds since Unix epoch in C#?

You can start to calculate this manually but C# has built-in support for this.

A first way to achieve our goal is through the DateTimeOffset.ToUnixTimeMilliseconds() method:

And if you really want to calculate this yourself:

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