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Date regex tester: dd/mm/yyyy, mm/dd/yyyy and ISO

Choose a date format, test one value per line and copy the JavaScript regex or HTML pattern. Compare format checks with strict ranges and a leap-year aware ISO pattern before validating real calendar dates on your server.

All 8 date regex patterns

All formats require leading zeros. Range and calendar patterns use years 0001-9999. Passing a format-only pattern does not guarantee a real date.

Regex vs <input type="date">

A populated native date input always submits YYYY-MM-DD whatever the user's locale, even when the picker displays day first or month first. These ISO patterns cover four-digit years; HTML also permits longer positive years. Use min and max for date bounds and required to prevent empty values.

<label for="date">Date</label>
<input id="date" name="date" type="date" min="2026-01-01" max="2026-12-31" required>

The pattern attribute applies to text fields, not date inputs. Use a text input only when you need an explicit format such as dd/mm/yyyy, with a clear label and format hint. Regex checks text; the native date control also checks calendar validity.

See the HTML Standard date input specification for native date behavior.

Validate the date on the server too

A format regex can't fully check February 29. Even the strict range pattern accepts 2023-02-29 and April 31. A JS Date round-trip check is needed after matching the expected format: JavaScript normalizes impossible dates, so compare the resulting year, month and day to the originals.

function isRealDate(y, m, d) {
  if (![y, m, d].every(Number.isInteger) || y < 1 || y > 9999) return false;
  const date = new Date(0);
  date.setUTCFullYear(y, m - 1, d);
  return date.getUTCFullYear() === y &&
    date.getUTCMonth() === m - 1 && date.getUTCDate() === d;
}

// Match the expected format before converting the components.
const match = /^([0-9]{4})-([0-9]{2})-([0-9]{2})$/.exec(value);
const valid = match !== null && isRealDate(...match.slice(1).map(Number));

The leap-year aware ISO regex encodes Gregorian calendar rules, including centuries divisible by 400. The helper expresses calendar validation more clearly. UTC components avoid daylight-saving changes, and setUTCFullYear preserves years below 100. For slash formats, extract the components in the order you selected; do not rely on new Date(value) to guess a locale. Reject invalid values before storing them, then check permitted ranges and business rules on the server.

Date regex FAQ

Date and time fields

Need a time as well? See input type=datetime-local for local date and time values without a time zone.