Replacing moment() with dayjs

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

...which is not in locale format.

Also, trying any variation of .month() I am always getting results in the number of the month. But I cannot get the name.

As mentioned in the Days JS github readme, you have to import the internationalisation that you intent to use, it will not be included by default. So I wrote a simple program to check this and it worked

const dayjs = require('dayjs')
import 'dayjs/locale/nb'

describe('SO Ques', () => {
  it('SO Ques', () => {
    cy.log(dayjs().locale('nb').add(2, 'Month').format('MMMM'))
  })
})

Test Runner:

So your program should look like:

const dayjs = require('dayjs')
import 'dayjs/locale/nb'

public day() {        
    return dayjs().locale('nb');
}
const in2Months = page.day().add(2, 'Month').format('MMMM');

You can evaluate all the values in a function and then return it and then use it in your test like this:

function date() {
    return {
        day: dayjs().locale('nb').add(2, 'Month').format('DD'),
        month: dayjs().locale('nb').add(2, 'Month').format('MMMM'),
        year: dayjs().locale('nb').add(2, 'Month').format('YYYY'),
    };
}

date().day //28
date().month //mars
date().year //2022