Can I make node.js Date always be in UTC/GMT?

From the MDN docs on Date#getTime:

The value returned by the getTime method is the number of milliseconds since 1 January 1970 00:00:00 UTC.

Assuming you're storing dates/times as numbers (which I would recommend), getTime is already UTC, always.

Suppose your client then requests a date from the server. If the server provides the date as a number, the client can then do:

new Date(timestamp);

And it will be correctly adjusted to the local time on the client.

Of course, maybe I'm misunderstanding your problem. But I just want to point out that this...

new Date().getTime() + new Date().getTimezoneOffset();

...should never really make sense. It's taking a UTC-based time and then offsetting it further, in essence double-offsetting a time.

You can use TZ configuration parameter of node.js as follows.

For bash (and related)

export TZ=UTC

For Powershell

$env:TC = 'UTC'

Then for both:

nodejs server/index.js