Intl.DateTimeFormat

const date = new Date(Date.UTC(2020, 11, 20, 3, 23, 16, 738));
// Results below assume UTC timezone - your results may vary

// Specify default date formatting for language (locale)
console.log(new Intl.DateTimeFormat("en-US").format(date));
// Expected output: "12/20/2020"

// Specify default date formatting for language with a fallback language (in this case Indonesian)
console.log(new Intl.DateTimeFormat(["ban", "id"]).format(date));
// Expected output: "20/12/2020"

// Specify date and time format using "style" options (i.e. full, long, medium, short)
console.log(
  new Intl.DateTimeFormat("en-GB", {
    dateStyle: "full",
    timeStyle: "long",
    timeZone: "Australia/Sydney",
  }).format(date),
);
// Expected output: "Sunday, 20 December 2020 at 14:23:16 GMT+11"

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

//       ,
//        
console.log(new Intl.DateTimeFormat().format(date));
// "12/19/2012",      en-US    America/Los_Angeles

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

//   ,     
// America/Los_Angeles   

//      --
console.log(new Intl.DateTimeFormat("en-US").format(date));
// "12/19/2012"

//      --
console.log(new Intl.DateTimeFormat("en-GB").format(date));
// "20/12/2012"

//     --
console.log(new Intl.DateTimeFormat("ko-KR").format(date));
// "2012. 12. 20."

//        
console.log(new Intl.DateTimeFormat("ar-EG").format(date));
// "//"

//        ,
//   2012   24-   
console.log(new Intl.DateTimeFormat("ja-JP-u-ca-japanese").format(date));
// "24/12/20"

//      , 
// ,    ,    
console.log(new Intl.DateTimeFormat(["ban", "id"]).format(date));
// "20/12/2012"

const date = new Date(Date.UTC(2012, 11, 20, 3, 0, 0, 200));

//        
let options = {
  weekday: "long",
  year: "numeric",
  month: "long",
  day: "numeric",
};
console.log(new Intl.DateTimeFormat("de-DE", options).format(date));
// "Donnerstag, 20. Dezember 2012"

//     UTC   
options.timeZone = "UTC";
options.timeZoneName = "short";
console.log(new Intl.DateTimeFormat("en-US", options).format(date));
// "Thursday, December 20, 2012, GMT"

//    
options = {
  hour: "numeric",
  minute: "numeric",
  second: "numeric",
  timeZone: "Australia/Sydney",
  timeZoneName: "short",
};
console.log(new Intl.DateTimeFormat("en-AU", options).format(date));
// "2:00:00 pm AEDT"

//     
options.fractionalSecondDigits = 3; //      
console.log(new Intl.DateTimeFormat("en-AU", options).format(date));
// "2:00:00.200 pm AEDT"

//      24-  
options = {
  year: "numeric",
  month: "numeric",
  day: "numeric",
  hour: "numeric",
  minute: "numeric",
  second: "numeric",
  hour12: false,
  timeZone: "America/Los_Angeles",
};
console.log(new Intl.DateTimeFormat("en-US", options).format(date));
// "12/19/2012, 19:00:00"

//   ,     ,   undefined
console.log(new Intl.DateTimeFormat(undefined, options).format(date));
// "12/19/2012, 19:00:00"

//     
options = { hour: "numeric", dayPeriod: "short" };
console.log(new Intl.DateTimeFormat("en-US", options).format(date));
// 10 at night

const options = { calendar: "chinese", numberingSystem: "arab" };
const dateFormat = new Intl.DateTimeFormat(undefined, options);
const usedOptions = dateFormat.resolvedOptions();

console.log(usedOptions.calendar);
// "chinese"

console.log(usedOptions.numberingSystem);
// "arab"

console.log(usedOptions.timeZone);
// "America/New_York" (the users default timezone)