JS Dates

JS Dates

The Date object is used to work with dates and times in JavaScript.

const now = new Date();
console.log(now);

You can also create specific dates.

const d1 = new Date("2025-01-01");
const d2 = new Date(2025, 0, 1); // Month is 0-based (0 = January)

console.log(d1);
console.log(d2);

JS Date Formats

JavaScript supports ISO format (recommended) and local string formats.

const date = new Date();

console.log(date.toISOString());
console.log(date.toDateString());
console.log(date.toTimeString());

ISO format (YYYY-MM-DD) is safest when parsing dates.

const isoDate = new Date("2025-03-10");
console.log(isoDate);

Avoid ambiguous formats like 03/10/2025 because they depend on locale.

JS Date Get

You can retrieve parts of a date using get methods.

const d = new Date();

console.log(d.getFullYear());
console.log(d.getMonth());     // 0-11
console.log(d.getDate());
console.log(d.getDay());       // 0-6
console.log(d.getHours());
console.log(d.getMinutes());
console.log(d.getSeconds());

Use UTC versions when working with international time.

console.log(d.getUTCFullYear());
console.log(d.getUTCMonth());

JS Date Set

You can modify parts of a date using set methods.

const date2 = new Date();

date2.setFullYear(2030);
date2.setMonth(5);
date2.setDate(15);

console.log(date2);

Timestamps

A timestamp represents milliseconds since January 1, 1970 (Unix Epoch).

const timestamp = Date.now();
console.log(timestamp);

const fromTimestamp = new Date(timestamp);
console.log(fromTimestamp);

JS Date Methods

Commonly used Date methods include:

const dt = new Date();

console.log(dt.toLocaleDateString());
console.log(dt.toLocaleTimeString());
console.log(dt.toUTCString());
console.log(dt.valueOf());

UTC vs Local Time

JavaScript stores dates internally in UTC, but displays them in local time by default.

const example = new Date("2025-03-10T10:00:00Z");
console.log(example.toString());
console.log(example.toUTCString());

Modern Formatting with Intl

Use Intl.DateTimeFormat for proper localization.

const formatter = new Intl.DateTimeFormat("en-US", {
  year: "numeric",
  month: "long",
  day: "2-digit"
});

console.log(formatter.format(new Date()));

Important Note

The built-in Date API has limitations. For complex time-zone handling, consider modern libraries or the upcoming Temporal API.

Next Step

Continue with JS Arrays to work with collections of data.