How to Match a Date with Regex (Multiple Formats)

The practical regex for ISO 8601 dates (YYYY-MM-DD): ^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$. It rejects month 13, day 32, and the all-zeros date. There are equivalent patterns for US-style MM/DD/YYYY, EU-style DD/MM/YYYY, relaxed forms that accept single-digit months, and a common ISO-style timestamp with time. Below I walk all of them, with runnable code in JavaScript, Python, and PHP, engine notes, common bugs, and calendar validation after the format check.

The compact patterns here do not reject 2025-02-30 or enforce leap years. A more complex regex can encode those rules, but a strict date parser is easier to maintain. Regex narrows the input to "date-shaped"; the parser confirms it is a real day.

The executable validators below use years 0001–9999. The short shape regex alone also accepts year 0000; whether that year is meaningful depends on the calendar convention and parser.

Quick reference

ISO 8601 date:

^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$

US (MM/DD/YYYY):

^(0[1-9]|1[0-2])\/(0[1-9]|[12][0-9]|3[01])\/\d{4}$

EU (DD/MM/YYYY):

^(0[1-9]|[12][0-9]|3[01])\/(0[1-9]|1[0-2])\/\d{4}$

Common ISO-style datetime shape with timezone:

^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])T(?:[01]\d|2[0-3]):[0-5]\d:[0-5]\d(?:\.\d+)?(?:Z|[+-](?:[01]\d|2[0-3]):[0-5]\d)$

Use one explicit input format. 09/10/2026 is ambiguous without knowing whether the first field is month or day. A date format regex should not guess the user's locale. For a timestamp, validate the offset, calendar date, and application-supported precision after the shape check; the example is not a complete implementation of every ISO 8601 representation.

ISO 8601 date (YYYY-MM-DD)

^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$

• \d{4} is a 4-digit year. To restrict to a sensible range, use (19|20)\d{2} for 1900-2099.
• (0[1-9]|1[0-2]) is the month: 01-09 or 10-12.
• (0[1-9]|[12][0-9]|3[01]) is the day: 01-09, 10-29, or 30-31.

This pattern accepts 2025-02-30 and 2025-04-31 (days that do not exist in those months). Use a date parser for maintainable calendar validation.

US format (MM/DD/YYYY)

^(0[1-9]|1[0-2])\/(0[1-9]|[12][0-9]|3[01])\/\d{4}$

Same month and day sub-patterns, year on the right, separator is /. To allow - or . as alternative separators: replace \/ with [\/\-.] (and use the same separator both times by capturing it: ([\/\-.]) ... \1).

EU format (DD/MM/YYYY)

^(0[1-9]|[12][0-9]|3[01])\/(0[1-9]|1[0-2])\/\d{4}$

Same components as US, day-first instead of month-first. The classic ambiguity: 01/02/2025 could be January 2nd (US) or February 1st (EU). Always know which format your input is in before validating.

Relaxed: single-digit months and days

If the input might be 2025-2-9 (not zero-padded):

^\d{4}-(0?[1-9]|1[0-2])-(0?[1-9]|[12][0-9]|3[01])$

The ? after the leading zero makes it optional, so both 02 and 2 match.

ISO 8601 datetime with time and timezone

This pattern covers the timestamp shape used by examples like 2025-10-29T14:32:07Z or 2025-10-29T14:32:07-05:00:

^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])T(?:[01]\d|2[0-3]):[0-5]\d:[0-5]\d(?:\.\d+)?(?:Z|[+-](?:[01]\d|2[0-3]):[0-5]\d)$

The added parts:

• T separator between date and time.
• (?:[01]\d|2[0-3]) for hour (00-23).
• :[0-5]\d:[0-5]\d for minutes and seconds (00-59).
• (?:\.\d+)? for optional fractional seconds.
• (?:Z|[+-](?:[01]\d|2[0-3]):[0-5]\d) for the timezone: either Z for UTC or a +HH:MM / -HH:MM offset.

Examples in JavaScript, Python, and PHP

JavaScript:

const isoDate = /^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$/;

function isValidIsoDate(input) {
  if (typeof input !== "string" || !isoDate.test(input) || input.startsWith("0000-")) return false;
  // Belt-and-braces: ensure it parses as a real date too
  const d = new Date(input);
  return !isNaN(d.getTime()) && input === d.toISOString().slice(0, 10);
}

isValidIsoDate("2025-10-29");  // true
isValidIsoDate("2025-02-30");  // false (regex passes, Date check fails)
isValidIsoDate("2025-13-01");  // false (regex fails)

Python:

import re
from datetime import datetime

ISO_DATE = re.compile(r"^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$")

def is_valid_iso_date(value: str) -> bool:
    if not ISO_DATE.fullmatch(value):
        return False
    try:
        datetime.strptime(value, "%Y-%m-%d")
        return True
    except ValueError:
        return False

is_valid_iso_date("2024-02-29")  # True (leap year)
is_valid_iso_date("2023-02-29")  # False (not a leap year)

PHP:

function isValidIsoDate(string $value): bool {
    if (str_starts_with($value, '0000-') || preg_match('/\A[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])\z/', $value) !== 1) {
        return false;
    }
    $d = DateTime::createFromFormat('Y-m-d', $value);
    return $d !== false && $d->format('Y-m-d') === $value;
}

The pattern catches obvious format errors instantly; the date parser catches "valid format, impossible date" cases like February 30 or 2023-02-29.

Engine compatibility

Character classes and alternation are widely supported, but \d, delimiter escaping, and ending anchors differ across engines. Use [0-9] when the format requires ASCII digits, and a whole-string check before parsing.

I prefer fromisoformat in Python 3.11+ and LocalDate.parse in Java: they both reject 2025-02-30 automatically without needing the round-trip check.

Common mistakes

The bugs I see most often.

Trusting this short regex to validate the actual day. It only checks the listed field ranges. 2025-02-30 and 2025-04-31 match the regex but those days do not exist. Always pair the regex with a date parser if the input has to be a real day.

Two-digit years. Patterns like ^\d{2}-\d{2}-\d{2}$ accept 25-10-29 but you cannot tell if "25" is 1925 or 2025. Always require a 4-digit year unless you have a hard reason not to.

Hardcoded separators. A pattern with literal / rejects 2025-10-29 (hyphens). Either pick one format per input field, or use a character class [\/\-.] and capture it with a backreference to require both sides match.

Forgetting the anchors. \d{4}-\d{2}-\d{2} matches 2025-10-29extra because nothing pins the end. Always anchor for validation.

Locale-ambiguous parsing. 01/02/2025 could be January 2nd or February 1st depending on locale. Never accept this format from international users without an explicit locale signal.

Treating a passing regex as a parsed value. The regex returns true/false. It does NOT give you a usable Date object. Run the parser after the regex to get the actual date for arithmetic and comparison.

Calendar validation: leap years and days in each month

A sufficiently detailed regex can encode calendar rules, but the short patterns above intentionally leave these checks to a date parser:

• February 29 is only valid in years divisible by 4 (except century years not divisible by 400).
• February 30 and February 31 never exist.
• April, June, September, and November have 30 days; everything else has 31 except February.

To enforce these, run the regex first and then parse the string as a date in your language. If the parse succeeds and round-trips back to the same string, the date is real. This is the pattern shown in all three code examples above.

Test cases

FAQ

See also

• How to Match Numbers with Regex: year, month, and day are all bounded-range numbers
• How to Match an Email Address with Regex: the cousin field on every signup form
• Regex Anchors: why ^ and $ matter so much for date validation
• Regex Lookaheads and Lookbehinds: composing constraints like "must precede a time"
• Regex Capturing Groups and Backreferences: the \1 trick for "same separator on both sides"
• Regex Cheat Sheet: the wider syntax and engine compatibility reference

External reference: the ISO 8601 standard summary covers the full date-and-time formats. Try the patterns at regex101.com with your own input strings.