Check Whether a Date Is Valid in JavaScript

Last Updated : 1 Sep, 2026

JavaScript provides several ways to validate whether a given date is valid. The appropriate approach depends on whether you need to validate the date object itself, a specific date format, or both.

  • Check the date using getTime() and isNaN().
  • Use a custom validation method to verify the date and its format.
  • Use regular expressions when the input must follow a specific date format.

Approach 1: Using isNaN() and getTime()

The getTime() method returns the timestamp of a Date object. For an invalid date, it returns NaN. The isNaN() method can be used to determine whether the date is invalid.

Example: Checks whether a given date is valid using getTime() and isNaN().

JavaScript 
function isValidDate(date) {
    if (Object.prototype.toString.call(date) === "[object Date]") {
        if (isNaN(date.getTime())) {
            console.log("Invalid Date");
        }
        else {
            console.log("Valid Date");
        }
    }
}

// Driver code
const date = new Date("This is not date.");

isValidDate(date);

Output
Invalid Date

Approach 2: Using a Custom Method

A custom method can validate a date by checking whether its timestamp is valid and comparing the original date string with the normalized date representation. This helps ensure that the input represents the expected date.

Example: Validates a date string using a custom method.

JavaScript 
Date.prototype.isValid = function(dateString) {
    return !isNaN(this.getTime()) &&
        dateString === this.toISOString().slice(0, 10);
};

const dateString = "2012/2/30";
const date = new Date(dateString);

console.log(date.isValid(dateString));

Output
false

Approach 3: Using Regular Expressions

Regular expressions can be used to first verify that a date follows a specific format. After extracting the year, month, and day, a Date object can be created and compared with the original values to ensure that the date itself is valid.

Example: Validates dates in YYYY-MM-DD, DD/MM/YYYY, and MM-DD-YYYY formats.

JavaScript 
function isValidDateFormat(dateString, format) {
    let regex;

    // Define regex patterns for different date formats
    switch (format) {
        case 'YYYY-MM-DD':
            regex = /^\d{4}-\d{2}-\d{2}$/;
            break;

        case 'DD/MM/YYYY':
            regex = /^\d{2}\/\d{2}\/\d{4}$/;
            break;

        case 'MM-DD-YYYY':
            regex = /^\d{2}-\d{2}-\d{4}$/;
            break;

        default:
            return false;
    }

    // Check whether the format is correct
    if (!regex.test(dateString)) {
        return false;
    }

    // Parse date parts based on the format
    let day, month, year;

    switch (format) {
        case 'YYYY-MM-DD':
            [year, month, day] =
                dateString.split('-').map(Number);
            break;

        case 'DD/MM/YYYY':
            [day, month, year] =
                dateString.split('/').map(Number);
            break;

        case 'MM-DD-YYYY':
            [month, day, year] =
                dateString.split('-').map(Number);
            break;
    }

    // Create a Date object
    const date = new Date(year, month - 1, day);

    // Validate the date parts
    return date.getFullYear() === year &&
        date.getMonth() === month - 1 &&
        date.getDate() === day;
}

// Driver code
console.log(
    isValidDateFormat('2024-05-24', 'YYYY-MM-DD')
);

console.log(
    isValidDateFormat('24/05/2024', 'DD/MM/YYYY')
);

console.log(
    isValidDateFormat('05-24-2024', 'MM-DD-YYYY')
);

console.log(
    isValidDateFormat('2024/05/24', 'YYYY-MM-DD')
);

Output
true
true
true
false
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