Why new Date(null) is returning this: Date 1970-01-01T00:00:00.000Z?

Question

new Date(null)
// Date 1970-01-01T00:00:00.000Z

How come when I type new Date(null) in JavaScript console I'm getting
Date 1970-01-01T00:00:00.000Z?

Answer 1

Because the ECMAScript 2017 standard says so?

The end of ECMA section 20.3.1.1 claims:

The exact moment of midnight at the beginning of 01 January, 1970 UTC is represented by the value +0.

...which might make you say, "...but!, but!, I did not say +0, I said":

new Date(null)

Ok, so let's follow the standard on that one...

That Date constructor example goes to section 20.3.2.2, where item 3.b.iii there says:

3.b.iii: Else, let V be ToNumber(v).

ToNumber is a hyperlink, so follow that to section 7.1.3 where there is a number conversion table that shows:

Argument Type  | Result
Null                       | +0

Therefore:

new Date(null)

Effectively becomes:

new Date(+0)

Which is why you ultimately get:

Date 1970-01-01T00:00:00.000Z