MediumDates4 min read

US Date Regex (MM/DD/YYYY)

Validates a calendar date in the US MM/DD/YYYY format with slash separators, requiring zero-padded month and day values.

#date#us-format#validation#dates#calendar#forms

Regex Pattern

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

Pattern Breakdown

Hover over a token to see what it does.

^(0[1-9]|1[0-2])/(0[1-9]|[12]\d|3[01])/\d{4}$
TokenMeaning
^Anchors the match to the start of the string.
(0[1-9]|1[0-2])The month: 01-09 or 10-12.
/A literal forward slash separating the date components.
(0[1-9]|[12]\d|3[01])The day: 01-09, 10-29, or 30-31.
\d{4}Exactly four digits for the year.
$Anchors the match to the end of the string.

Detailed Explanation

What it does

This pattern matches dates written in the US convention MM/DD/YYYY, such as 07/10/2026. It requires a zero-padded two-digit month between 01 and 12, a zero-padded two-digit day between 01 and 31, and a four-digit year, all separated by forward slashes.

Why it works

The month and day are each validated with their own alternation of digit ranges rather than a generic `\d{2}`, which keeps invalid values like month 13 or day 32 out. Because regex has no calendar awareness, the day range 30-31 is accepted regardless of which month precedes it, so month-specific day limits and leap years are not enforced.

Common use cases

  • Validating US-formatted date fields in web and desktop forms
  • Pre-checking spreadsheet or CSV imports that use MM/DD/YYYY dates
  • Filtering log files or filenames that embed a US-style date
  • Guarding a date parser input before handing it to a full date library

Edge cases

  • 02/30/2026 matches even though February never has 30 days, because the pattern only checks digit ranges
  • 04/31/2026 matches even though April has only 30 days, since month-day correlation isn't representable with this regex alone
  • Single-digit months or days without a leading zero, like 1/5/2026, correctly fail to match
  • Two-digit years such as 01/15/26 correctly fail because exactly four digits are required for the year

Limitations

  • Does not validate real calendar correctness, such as leap years or month-specific day counts
  • Only supports the slash-separated MM/DD/YYYY order, not other regional orderings like DD/MM/YYYY
  • Does not support a time component or timezone information

Interactive Tester

Edit the pattern or text below — matching runs live in your browser.

//
Open in Playground →
01/15/2026 12/31/2025 02/30/2026
3 matches· capture groups: 2

Test Cases

Editable — add your own inputs to see if they pass.

InputExpectedResult
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass

Language Variants

Production-ready examples in 12 languages.

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

function isValidUsDate(value) {
  return usDatePattern.test(value);
}

console.log(isValidUsDate("07/10/2026")); // true

Common Mistakes

Assuming a regex match guarantees a real calendar date, so invalid combinations like 02/30 slip through.

Fix: Use the regex as a format pre-check only, then parse with a date library and confirm the value round-trips to the same date.

Forgetting that this pattern requires zero-padded month and day, rejecting inputs like 7/10/2026.

Fix: Either pre-pad user input with leading zeros before validating, or relax the groups to `\d{1,2}` if single digits should be accepted.

Confusing MM/DD/YYYY with the DD/MM/YYYY order used in many other locales.

Fix: Clearly label the expected format in the UI, or detect locale and swap to a DD/MM/YYYY variant when appropriate.

Performance Notes

  • All quantifiers are bounded (`{4}`, fixed alternation branches), so matching runs in linear time with no catastrophic backtracking risk.
  • Anchors at both ends let the engine reject wrong-length input immediately.
  • The month and day alternations are mutually exclusive by leading digit, so backtracking between branches is minimal.

Browser Compatibility

EngineSupportedNotes
ChromeYes—
FirefoxYes—
SafariYes—
EdgeYes—
Node.jsYes—

Work with this pattern

Take this expression further — test it against your own data, adapt it in the builder, or read up on the syntax behind it.

Regex Tester

Test a regular expression against sample text and see every match highlighted live.

Regex Generator

Build a pattern by clicking blocks — no syntax memorisation required.

Regular Expressions Guide

What regex is, how the syntax works, and the mistakes that trip people up.

Regex Cheat Sheet

Every token, quantifier, and assertion on one printable page.

Python Regex Guide

The re module end to end — search, match, findall, groups, and substitution.

Regex Pattern Library

100+ ready-to-use patterns for email, URLs, dates, IPs, and more.