Cypress - replaceing moment() with dayjs

Question

I'm having problems with the locale when going from the deprecated Moment to DayJS in Cypress.

The original Moment() usage:

public moment(): Moment {
    const moment = Cypress.moment();
    moment.locale("nb-NO");
    return moment;
}

const in2Months = moment().add(2, "months");

This worked fine, and for instance "March" was replaced by "Mars".

However, when trying to use it the same way with days.js, the locale isn't changed:

public day() {        
    return dayjs().locale('nb-NO');
}

const in2Months = page.day().add(2, "months");

The result here is still "March". I've tried using just 'no' for the locale, with the same result.

What am I missing here?

UPDATE: As per the below answer:

import dayjs from "dayjs";
import 'dayjs/locale/nb'

const in2Months = dayjs().locale('nb').add(2, 'Month');

cy.log(in2monthstoString());

RESULT: Mon, 28 Mar 2022 12:39:29 GMT

Not local format.

Also, trying any variation of .month() I can find allways results in the number of the month. I cannot get the name.