Running prettifier gives UTC date instead of local time + offset

[harmtemolder]

I have set the Header template to:

modified: {{date:YYYY-MM-DDTHH:mm:ssZ}}

The preview next to that input box shows this:

modified: 2021-03-10T08:58:54-03:00

But when I run prettifier I get this:

modified: 2021-03-10T11:59:56.000Z

How come it’s now in UTC instead of with my local offset?