Parsing

As local time

const date = new Date(2012, 11, 20, 3, 0, 0)

As UTC time

const date = new Date(Date.UTC(2012, 11, 20, 3, 0, 0))

From ISO strings

const date = new Date('2018-04-20T12:00:00Z')

Note that JavaScript doesn’t “store” timezones in a date object. All these date objects, when expressed via .toString() or similar, will show the local timezone of the browser, regardless if you parsed UTC dates.

Formatting dates

Default formatting

console.log(new Intl.DateTimeFormat().format(date))
// → '12/19/2012' (assuming America/Los_Angeles)

Custom locale

console.log(new Intl.DateTimeFormat('en-GB').format(date))
// → '19/12/2012' (date-first)

Custom timezone

console.log(new Intl.DateTimeFormat('en-AU', {
  timeZone: 'Australia/Sydney'
}).format(date))
// → '19/12/2012'

Custom formats

Time

console.log(new Intl.DateTimeFormat('default', {
  hour: 'numeric',
  minute: 'numeric',
  second: 'numeric'
}).format(date))
// → '2:00:00 pm'

Date

console.log(new Intl.DateTimeFormat('en-US', {
  year: 'numeric',
  month: 'numeric',
  day: 'numeric'
}).format(date))
// → '12/19/2012'

To specify options without a locale, use 'default' as a locale.

All options

{
  weekday: 'narrow' | 'short' | 'long',
  era: 'narrow' | 'short' | 'long',
  year: 'numeric' | '2-digit',
  month: 'numeric' | '2-digit' | 'narrow' | 'short' | 'long',
  day: 'numeric' | '2-digit',
  hour: 'numeric' | '2-digit',
  minute: 'numeric' | '2-digit',
  second: 'numeric' | '2-digit',
  timeZoneName: 'short' | 'long',

  // Time zone to express it in
  timeZone: 'Asia/Shanghai',
  // Force 12-hour or 24-hour
  hour12: true | false,

  // Rarely-used options
  hourCycle: 'h11' | 'h12' | 'h23' | 'h24',
  formatMatcher: 'basic' | 'best fit'
}