JavaScript Date Formats

Date formatting runs in two directions. Input: which text strings JavaScript can reliably turn into a Date. Output: how to turn a Date back into text that people (or other programs) can read.

// Input: The Safe Format Is ISO

ISO 8601 (year-month-day, largest unit first) is the only string format every browser is guaranteed to read the same way:

Shorter ISO strings

ISO dates can leave off the day, or the month and day. The missing parts become the 1st, at midnight UTC, so in the Americas the result lands on the evening before:

console.log(new Date("2015-03").toString());    // March 1, UTC
console.log(new Date("2015").toString());       // January 1, UTC

Date and time are separated by a capital T, and a capital Z means UTC. Leaving out the T or Z in a date-time string can give different results in different browsers.

// Input: Other Formats

Browsers also accept two other kinds of string. They usually work, but they are not part of the standard, so behavior can vary:

Long dates are forgiving: the month and day can be in either order, the month can be full or abbreviated, commas are ignored, and case does not matter. new Date("JANUARY, 25, 2015") works.

// Date.parse()

Date.parse() reads a date string and returns its timestamp in milliseconds, instead of a Date object. You can then pass that number to new Date():

let msec = Date.parse("March 21, 2012");
console.log(msec);
console.log(new Date(msec).toDateString());

(The exact number depends on your time zone.) It follows the same rules as new Date(string), including returning NaN for a string it cannot read.

// Output: Built-in String Methods

const d = new Date(2026, 9, 2, 14, 30);

d.toString()       // "Fri Oct 02 2026 14:30:00 GMT-0400 (Eastern Daylight Time)"
d.toDateString()   // "Fri Oct 02 2026"
d.toTimeString()   // "14:30:00 GMT-0400 (Eastern Daylight Time)"
d.toISOString()    // "2026-10-02T18:30:00.000Z"
d.toUTCString()    // "Fri, 02 Oct 2026 18:30:00 GMT"

Notice toISOString and toUTCString show 18:30. They always convert to UTC, which is four hours ahead of Eastern Daylight Time.

// Output for People: toLocaleDateString

The toLocale... methods format a date the way people in a given region expect. Pass a locale code:

d.toLocaleDateString("en-US")   // "10/2/2026"   (United States)
d.toLocaleDateString("en-GB")   // "02/10/2026"  (United Kingdom)
d.toLocaleDateString("de-DE")   // "2.10.2026"   (Germany)
d.toLocaleTimeString("en-US")   // "2:30:00 PM"

// Choosing the Pieces with Options

A second argument controls exactly which parts appear and how:

d.toLocaleDateString("en-US", {
  weekday: "long", year: "numeric", month: "long", day: "numeric"
});
// "Friday, October 2, 2026"

d.toLocaleDateString("en-US", { month: "short", day: "numeric" });
// "Oct 2"

d.toLocaleTimeString("en-US", { hour: "numeric", minute: "2-digit" });
// "2:30 PM"

// Showing Another Time Zone

d.toLocaleTimeString("en-US", { timeZone: "Europe/London", hour: "numeric", minute: "2-digit" });
// "7:30 PM"  (the same moment, on a clock in London)

// Building a Custom Format

For an exact fixed pattern like YYYY-MM-DD in local time, build it from the parts (covered fully in Date Get):

function ymd(date) {
  const y = date.getFullYear();
  const m = String(date.getMonth() + 1).padStart(2, "0");
  const day = String(date.getDate()).padStart(2, "0");
  return `${y}-${m}-${day}`;
}

console.log(ymd(d));

// Which Format When?

// Quick Check

const d = new Date(2026, 9, 2);
console.log(d.toLocaleDateString("en-US", { month: "long", day: "numeric" }));

// Try It

▶ Open Playground

1. Click Open Playground. Format today's date in "en-US", "en-GB", and "ja-JP"
2. Produce "Friday, October 2" (no year) using options
3. Show what time it is right now in Tokyo using timeZone: "Asia/Tokyo"
4. Save a date with toISOString(), then read it back with new Date() and confirm the times match