moment.updateLocale('en', {
    eras: {
        since:  String,              
        until:  +Infinity/-Infinity, 
        offset: 1,                   
        name:   'Anno Domini/Before Christ', 
        narrow: 'AD/BC',
        abbr:   'AD/BC'
    },
});

npm install moment 

// Acquiring the plugin
const moment = require("moment");
 
let era = moment.updateLocale("en", {
    eras:
    {
        until: -Infinity,
        since: "0000-05-16",
        offset: 1,
        name: "Before Christ",
        narrow: "BC",
        abbr: "BC",
    },
});
 
console.log("Name of the era is:", era._eras.name);
console.log("Abbreviation of the era is:", era._eras.abbr);
console.log("This era is since:", era._eras.since);
console.log("It will last until:", era._eras.until);

Name of the era is: Before Christ
Abbreviation of the era is: BC
This era is since: 0000-05-16
It will last until: -Infinity

// Acquiring the plugin
const moment = require("moment");
 
let era = moment.updateLocale("en", {
    eras: {
        since: "0001-01-01",
        until: +Infinity,
        offset: 1,
        name: "Anno Domini",
        narrow: "AD",
        abbr: "AD",
    },
});
 
console.log("Name of the era is:", era._eras.name);
console.log("Abbreviation of the era is:", era._eras.abbr);
console.log("This era is since:", era._eras.since);
console.log("It will last until:", era._eras.until);

Name of the era is: Anno Domini
Abbreviation of the era is: AD
This era is since: 0001-01-01
It will last until: Infinity