Date Format Converter
Type a date in whatever form you have, and get every other notation.
How it works
The converter parses a date written in almost any common notation and rewrites it in the others: ISO 8601, day-first, month-first, long form with a written month name, and the abbreviated forms in between.
The difficult part is ambiguity rather than parsing. 03/04/2026 is 3 April to most of the world and 4 March in the United States, and nothing within the string resolves which was meant. Where a date can be read two ways the tool says so and shows both, because a silent assumption is precisely how date bugs reach production and survive there.
ISO 8601 exists to remove that problem. Written YYYY-MM-DD it sorts correctly as plain text, it means the same thing in every locale, and it is what belongs in filenames, databases, exports and anything another program will read.
Month and weekday names are produced through your browser's own locale data, so they appear in the language of the page rather than needing a separate translation, and unusual calendars and scripts are handled by the same mechanism.
Examples
An ambiguous date. 03/04/2026 is 3 April in most of the world and 4 March in the United States. The converter shows both readings rather than silently choosing one.
Preparing a filename. Convert to ISO 8601 — 2026-04-03 — and files sort chronologically without any special handling.
Reading a foreign format. Paste a date written with month names in another language and it is parsed through your browser's locale data.
Practical notes
The fundamental problem is that a bare numeric date can be genuinely ambiguous. 03/04/2026 is 3 April to most of the world and 4 March in the United States, and nothing in the string resolves it. Where ambiguity exists the tool says so rather than guessing, because a silent wrong guess is how date bugs reach production.
Use ISO 8601 — YYYY-MM-DD — for anything a machine will read. It sorts correctly as plain text, it is unambiguous in every locale, and it removes the whole class of problem in filenames, databases and exports.
Month and weekday names are rendered through your browser's locale data, so they appear in the language of the page rather than being translated separately.
Frequently asked questions
Why is ISO 8601 recommended?
It is unambiguous, sorts correctly as plain text, and is the format every programming language accepts without configuration.
Can I paste a long-form date?
Yes. Forms such as “11 August 2026” and “August 11, 2026” are both understood.
Why does it refuse to guess on 03/04/2026?
Because a wrong guess is worse than a question. Day-first and month-first orders are both in wide use, and a silent assumption is exactly how date bugs reach production.
Which format should I use for filenames?
ISO 8601, written YYYY-MM-DD. Files then sort into chronological order automatically, with no special handling.
Which format should I store dates in?
ISO 8601, written YYYY-MM-DD. It sorts correctly as text, it is unambiguous in every locale, and it removes an entire class of bug from exports and filenames.
Can it read dates with month names?
Yes, in the languages your browser has locale data for. Numeric formats are the ambiguous ones; a written month name resolves the order by itself.
What about two-digit years?
They are genuinely ambiguous and always have been. Interpretation depends on an assumed century window, so prefer four digits anywhere the value will be stored or exchanged.
Does it change my system settings?
No. It only reformats the text you give it. Your operating system and browser locale are untouched.
Can I convert a whole list of dates?
One at a time here. For bulk work, settle on ISO 8601 and use a spreadsheet or script, since the ambiguity rules need deciding once rather than per row.
Why do American and European dates differ?
Historical convention rather than logic. Month-first reflects how the date is spoken aloud in American English; day-first follows ascending order of magnitude. Neither is wrong, which is exactly why a numeric date alone cannot be trusted between the two.
Does the order of day and month matter in ISO 8601?
ISO 8601 fixes it: year, then month, then day, largest unit first. That ordering is what makes the format sort correctly as plain text and is the main reason to prefer it.
Guides on this topic
- ISO 8601, the date format that sorts itself How to read and write ISO 8601 dates, times, offsets, week dates, ordinal dates and durations, what the Z means, and how RFC 3339 differs.
- How to store dates and times correctly When to store UTC, when to store local time with a zone name, why offsets alone are not enough, which database types to use, and the parsing traps in JavaScript.