What is a Invalid Date?

An Invalid Date object is silently created when new Date() receives a string it cannot parse. Operations on it return NaN or throw a RangeError. JavaScript's Date constructor is lenient about what it accepts, but the accepted formats vary across browsers.

Why it happens

• •Passing a date string in DD/MM/YYYY format, which is not reliably parsed.
• •Passing an empty string or null to new Date().
• •Using a locale-specific format that the browser does not recognize.
• •Receiving a date from a user input or API that is malformed.

Examples

const d = new Date("31/12/2024"); // wrong format
console.log(d.toISOString());

RangeError: Invalid time value

// Use ISO 8601 format: YYYY-MM-DD
const d = new Date("2024-12-31");
console.log(d.toISOString()); // "2024-12-31T00:00:00.000Z"

// Always validate first
function parseDate(str) {
  const d = new Date(str);
  return isNaN(d.getTime()) ? null : d;
}

Related errors

• NaN in Arithmetic
• TypeError