Date Formatter

How to Use the Date Formatter

1. Pick a date and time in the date/time picker at the top. The picker defaults to "now" so you can see every format populated instantly.
2. Scan the 12-row table of outputs: ISO 8601, RFC 2822, US MM/DD/YYYY, EU DD/MM/YYYY and DD.MM.YYYY, long human-readable ("Monday, January 1, 2024"), short ("Jan 1, 2024"), Unix timestamp in seconds, Unix timestamp in milliseconds, relative ("3 days ago"), and locale-specific variants.
3. Click the copy button next to any row to grab that string into your clipboard.
4. Change the input to update every row at once - the formatter is reactive.

What Runs When You Change the Date

The component takes your date string, parses it into a JavaScript Date object, and then pipes it through twelve formatters in parallel. Most rows use Intl.DateTimeFormat with different options objects - that API is the one honest place in the browser where locale, timezone, and calendar rules actually behave correctly. The ISO 8601 row comes from toISOString(), which is RFC 3339-compliant. The RFC 2822 row comes from toUTCString(), which is the format email and HTTP Date headers specify. The Unix timestamp rows use Math.floor(date.getTime() / 1000) and date.getTime() directly. The "relative" row uses Intl.RelativeTimeFormat, which picks the largest unit that produces a readable phrase ("2 months ago" instead of "61 days ago") - a detail most handwritten solutions get wrong.

Real Situations Where the Right Format Matters

• Dropping a timestamp into a log line, a commit message, or a filename - ISO 8601 is the only choice that sorts correctly as a string.
• Writing the date into an email, invoice, or legal document where the reader's region expects DD/MM or MM/DD; getting it wrong on a contract with a March 5 vs. May 3 ambiguity has caused real litigation.
• Building an HTTP Last-Modified header or a cookie Expires attribute, both of which require RFC 2822/IMF-fixdate format.
• Passing a value into a database or API that stores BIGINT Unix milliseconds.
• Populating a CSV export for Excel where a bare ISO date gets mangled into "42736" serial numbers unless you quote it.
• Rendering a "posted 3 hours ago" line in a comment thread without pulling in Moment.js or date-fns.

Ambiguities the Formatter Cannot Fix for You

• 01/02/2024 is January 2 in the US, February 1 in the UK, and February 1 with dots in Germany. If the destination is ambiguous, pick ISO 8601 - 2024-02-01 has exactly one interpretation everywhere on Earth.
• Two-digit years (01/02/24) are a readability hazard and a Y2K-class bug magnet. Neither MM/DD/YY nor DD/MM/YY is offered here for that reason.
• Timezone implied vs. explicit. ISO 8601 with a trailing Z is UTC; without an offset it is local; "Jan 1, 2024 12:00 PM" could be any of the twenty-four zones currently in use (plus India's UTC+5:30, Nepal's UTC+5:45, and Iran's UTC+3:30).
• Non-Gregorian calendars. Intl.DateTimeFormat supports calendar: 'hebrew', islamic-umalqura, japanese, buddhist, and more - this tool sticks to Gregorian to keep the output table manageable, but the browser can do the others if you need them.
• "Relative" drifts with time. "3 days ago" becomes wrong tomorrow. Copy the absolute form if you are pasting into a document.

A Quick Tour of the Formats

ISO 8601 (first published 1988, current ISO 8601-1:2019) is the international standard; RFC 3339 is a stricter profile used in internet protocols, notably JSON-Schema date-times and OpenAPI. RFC 2822 (updated by RFC 5322) defines the "Mon, 01 Jan 2024 12:00:00 GMT" shape used in email headers; HTTP reuses a closely related format standardized by RFC 7231 as IMF-fixdate. Unix time dates to the first edition of Unix in 1971 and counts seconds since 1970-01-01T00:00:00Z; it ignores leap seconds and does not care about timezones, which is exactly why servers and databases adopted it. US MM/DD/YYYY is a holdover from hand-written checks; EU DD/MM/YYYY mirrors spoken order ("the 5th of January"); German DD.MM.YYYY uses dots because DIN 5008 said so. Knowing which audience you are writing for decides the right row.

When Native APIs Beat Libraries

For years the default answer was "just use Moment.js." Moment is now legacy (the maintainers themselves recommend moving off it) and it adds ~70 KB gzipped. date-fns is tree-shakable but still overkill for one-shot formatting. Day.js is the modern ~7 KB option with a Moment-like API. However, for the twelve common formats this tool produces, Intl.DateTimeFormat and Date methods in the browser are free, correctly localized, and maintained by the TC39 committee. This page skips the dependency entirely. Where libraries still shine: parsing loose user input ("next Tuesday at 3pm"), differential calendar math ("add 1 business month"), and timezone-aware arithmetic that outlives a single DST transition - the Temporal proposal (Stage 3 at TC39) will eventually cover those natively, but it is not yet shipping in stable browsers.