Date

const now = new Date();
const copy = new Date(now);
const fromString = new Date('2018-04-30'); // YYYY-MM-DDTHH:mm:ss.sssZ | YYYY-MM-DDTHH:mm:ss.sss+HH:mm
const tomorrow  = new Date(
  now.getFullYear(), now.getMonth(), now.getDate() + 1,
  now.getHours(), now.getMinutes(), now.getSeconds(), now.getMilliseconds(),
);
const yesterday = new Date(
  now.getFullYear(), now.getMonth(), now.getDate() - 1,
  now.getHours(), now.getMinutes(), now.getSeconds(), now.getMilliseconds(),
);

now.setFullYear(2024);
now.setMonth(2); // Starts from 0
now.setDate(14);
now.setHours(0);
now.setMinutes(3);
now.setSeconds(50);
now.setMilliseconds(727);

// UTC: YYYY-MM-DDTHH:mm:ss.sssZ
now.toISOString();

// Local: YYYY-MM-DDTHH:mm:ss.sss
(new Date(now.getTime() - (now.getTimezoneOffset() * 60000))).toISOString().slice(0, -1);

// YYYY/MM/DD HH:mm:ss
now.toLocaleString();

// YYYY-MM-DD (local timezone)
function formatDate(d) {
  const year = d.getFullYear();
  const month = String(d.getMonth() + 1).padStart(2, '0');
  const day = String(d.getDate()).padStart(2, '0');
  return [year, month, day].join('-');
}

const date = new Date(Date.UTC(2020, 11, 20, 3, 23, 16, 738));
const intl = new Intl.DateTimeFormat(locale, options);
intl.format(date);