📅 Date Format Converter: ISO 8601, US, European, Long and Unix
By Shihab Mia · Updated 2026-07-07
The date is treated as a calendar date (no time zone shift), so every format shows the same day.
A date format converter takes one calendar date and rewrites it in every common style at once. Enter a date here and it instantly shows ISO 8601 (YYYY-MM-DD), US (MM/DD/YYYY), European (DD/MM/YYYY), the long written form (Month D, YYYY), the Unix timestamp, and the day of the week. Copy whichever format you need with one click, no manual reformatting and no guessing whether 05/06 means the 5th of June or May the 6th.
What is the Date Format Converter?
A date is a single calendar day, but the way we write it down is far from universal. The same day, the sixth of May 2026, is written 2026-05-06 in ISO 8601, 05/06/2026 in the United States, and 06/05/2026 across most of Europe. Because the US puts the month first and Europe puts the day first, a string like 05/06/2026 is genuinely ambiguous unless you already know which convention produced it. That ambiguity is not a small edge case: it affects roughly the 330 million people who use month-first order in the US against the majority of the rest of the world who use day-first order. This tool removes the guesswork by showing one chosen day in all the major formats side by side.
ISO 8601 (YYYY-MM-DD) is the international standard published by the International Organization for Standardization, and it is the safest choice for anything technical. Its big-endian order, largest unit to smallest, means it sorts correctly as plain text: 2026-01-05 comes before 2026-11-02 in a simple alphabetical sort, which is exactly the chronological order you want. That single property is why databases, spreadsheets, APIs, log files and file names should use it. RFC 3339, the profile most web APIs and JSON payloads follow, is essentially ISO 8601 with a required time zone, so a value like 2026-05-06 that you produce here slots straight into either.
The US format (MM/DD/YYYY) and the European format (DD/MM/YYYY) both use two digit day and month fields separated by slashes, which is exactly what makes them collide. A quick rule of thumb: if the first number is greater than 12, the date must be day-first European order, because there is no 13th month. So 13/05/2026 can only be 13 May. But 05/06/2026 gives you no such clue, and that is the single most common source of date errors when data crosses borders. Some countries, notably Germany and much of central Europe, write the same day-first order with dots instead of slashes, as in 06.05.2026.
The long form (Month D, YYYY) spells the month out in words, so it can never be misread. Because it removes all ambiguity for a human reader, it suits letters, articles, contracts, invitations and printed documents where clarity matters more than sorting. The trade-off is that it does not sort or parse cleanly, so it belongs in prose, not in a data field.
The Unix timestamp is a different idea entirely. It is the number of whole seconds elapsed since 1 January 1970 at midnight UTC, the epoch that most computers count from. A value like 1735689600 is not human readable, but it is a single integer that stores a precise moment and is trivial to compare, sort and do arithmetic on, which is why code, logs and config files favour it. Note that many systems store the same value in milliseconds, giving a 13 digit number instead of 10, so watch the length when you paste a timestamp elsewhere.
This converter treats your input as a pure calendar date with no time-of-day and no time-zone offset, so every output describes the exact same day you picked. The Unix timestamp shown is that day at midnight UTC. The weekday is computed from the date itself using the Gregorian calendar rules the whole world uses for civil dates, so 19 June 2026, for example, always resolves to the correct day name no matter where you are reading this.
When to use it
- Rewriting a US date (MM/DD/YYYY) into the European order (DD/MM/YYYY) or vice versa without misreading the day and month.
- Converting a human date into ISO 8601 (YYYY-MM-DD) for a database field, spreadsheet column, file name or API request.
- Finding the Unix timestamp for a given calendar day to drop into code, a query filter or a config file.
- Looking up which day of the week a past or future date falls on for planning, invoicing or scheduling.
- Turning a plain date into the long written form (Month D, YYYY) for a letter, report, contract or invitation.
- Standardising mixed date columns from different regions into one consistent format before importing a spreadsheet.
How to use the Date Format Converter
- Pick a date in the date field, or click Use today to load the current date.
- Read off the same day in ISO 8601, US, European, long, weekday and Unix timestamp form, all at once.
- Click Copy next to any format to put that exact string on your clipboard.
- Change the date at any time and every format updates instantly, no reload needed.
Formula & method
Worked examples
You have the date 2024-06-19 and want it in every common format.
- ISO 8601: keep the parts in year, month, day order = 2024-06-19
- US: place month first, then day, then year = 06/19/2024
- European: place day first, then month, then year = 19/06/2024
- Long: spell the month and add the day and year = June 19, 2024
- Weekday: 19 June 2024 falls on a Wednesday
- Unix timestamp: seconds from 1970-01-01 UTC to 2024-06-19 midnight UTC = 1718755200
Result: ISO 2024-06-19, US 06/19/2024, EU 19/06/2024, long June 19, 2024, Wednesday, Unix 1718755200
You see the US date 12/25/2000 and want to confirm the day and other formats.
- Read it as US order: month 12, day 25, year 2000
- ISO 8601: 2000-12-25
- European: 25/12/2000
- Long: December 25, 2000
- Weekday: 25 December 2000 was a Monday
- Unix timestamp: 2000-12-25 midnight UTC = 977702400
Result: ISO 2000-12-25, EU 25/12/2000, long December 25, 2000, Monday, Unix 977702400
A spreadsheet cell shows 03/04/2025 and you are not sure if it is 3 April or March 4.
- Neither number is greater than 12, so the string alone cannot tell you the order
- Check the source: if it came from a US system, read it as US MM/DD/YYYY = March 4, 2025
- If it came from a UK or European system, read it as DD/MM/YYYY = 3 April 2025
- Enter the day you confirmed into the converter to lock it into unambiguous ISO 8601
- US reading gives ISO 2025-03-04; European reading gives ISO 2025-04-03
Result: The two readings are five weeks apart, which is exactly why converting to ISO 8601 first prevents errors.
The same day (1 January 2025) written in each format
| Format | Pattern | Output |
|---|---|---|
| ISO 8601 | YYYY-MM-DD | 2025-01-01 |
| US | MM/DD/YYYY | 01/01/2025 |
| European | DD/MM/YYYY | 01/01/2025 |
| German dot | DD.MM.YYYY | 01.01.2025 |
| Long | Month D, YYYY | January 1, 2025 |
| Compact | YYYYMMDD | 20250101 |
| Weekday | day name | Wednesday |
| Unix (seconds) | seconds since 1970 UTC | 1735689600 |
| Unix (milliseconds) | ms since 1970 UTC | 1735689600000 |
Where each date format is commonly used
| Format | Typical use |
|---|---|
| ISO 8601 (YYYY-MM-DD) | Databases, spreadsheets, APIs, file names, anything that must sort or stay unambiguous |
| US (MM/DD/YYYY) | Everyday writing in the United States |
| European (DD/MM/YYYY) | Everyday writing across most of Europe and much of the world |
| German dot (DD.MM.YYYY) | Germany, Austria, Switzerland and much of central Europe |
| Long (Month D, YYYY) | Letters, articles, contracts, invitations and printed documents |
| Unix timestamp | Code, logs and config files that store moments as a single number |
Default written date order by country or standard
| Region or standard | Order | Example for 6 May 2026 |
|---|---|---|
| United States | Month first | 05/06/2026 |
| United Kingdom and Ireland | Day first | 06/05/2026 |
| Most of Europe | Day first | 06/05/2026 |
| Germany and Austria | Day first, dots | 06.05.2026 |
| China, Japan, Korea | Year first | 2026-05-06 |
| ISO 8601 / RFC 3339 | Year first | 2026-05-06 |
Common mistakes to avoid
- Reading an ambiguous slash date the wrong way. A date like 05/06/2026 is May 6 in the US and 6 May in Europe. Always confirm which order the source uses before converting. If the first number is above 12 it must be day-first, but below that the string gives no clue.
- Expecting the Unix timestamp to include a time of day. This tool treats the input as a calendar day, so the Unix value is that day at midnight UTC. If you need a specific hour or minute, use a full date-and-time timestamp tool instead.
- Confusing seconds and milliseconds in a Unix timestamp. A 10 digit timestamp is in seconds; a 13 digit one is in milliseconds. Pasting a seconds value where a system expects milliseconds shifts the date to 1970, so always match the unit the target system wants.
- Assuming the weekday depends on your location. The day of the week is a property of the calendar date itself. 19 June 2026 is a Friday everywhere; it does not change with your time zone.
- Using a written or slash format in technical fields. Spreadsheets and databases sort and compare dates best in ISO 8601. Storing 06/19/2024 or June 19, 2024 in a data field often breaks sorting, filtering and parsing.
- Trusting a spreadsheet to auto-detect the order. Programs like Excel guess the order from your locale settings, so the same file can be read differently on two machines. Convert to ISO 8601 before importing to keep every reader in agreement.
Glossary
- ISO 8601
- The international date standard that writes dates as YYYY-MM-DD, which sorts correctly and reads the same everywhere.
- RFC 3339
- An internet profile of ISO 8601 used by most web APIs and JSON, essentially the same date format with a required time zone.
- Unix timestamp
- The number of whole seconds elapsed since 1 January 1970 at midnight UTC, used by computers to store a moment in time.
- Epoch
- The starting point a timestamp counts from. The Unix epoch is 1 January 1970 at midnight UTC.
- UTC
- Coordinated Universal Time, the global reference time zone with no daylight saving offset.
- Long date
- A date with the month spelled out, such as June 19, 2026, so it can never be misread.
- Big-endian date
- A date ordered largest unit first (year, month, day), like ISO 8601, which makes plain-text sorting match chronological order.
- Gregorian calendar
- The civil calendar used worldwide today, which fixes which weekday each date falls on.
Frequently asked questions
What is the ISO 8601 date format?
ISO 8601 writes a date as YYYY-MM-DD, for example 2026-06-19. It is the international standard because it is unambiguous worldwide and sorts correctly as plain text, which is why databases, spreadsheets and APIs prefer it.
What is the difference between US and European date formats?
The US format is MM/DD/YYYY (month first) while the European format is DD/MM/YYYY (day first). The same string can mean two different days, so 05/06/2026 is May 6 in the US and 6 May in Europe.
How do I convert MM/DD/YYYY to DD/MM/YYYY?
Swap the first two fields: the month and the day change places while the year stays put. So the US date 05/06/2026 becomes the European date 06/05/2026. Enter the date here and both orders are shown at once so you never swap the wrong numbers.
How do I convert a date to a Unix timestamp?
Pick the date and read the Unix timestamp field. It shows the number of seconds from 1 January 1970 at midnight UTC to your chosen day at midnight UTC. The converter calculates it for you automatically.
What does YYYY-MM-DD mean?
YYYY is the four digit year, MM is the two digit month (01 to 12), and DD is the two digit day (01 to 31). Written in that order with dashes it is the ISO 8601 standard, for example 2026-06-19 for 19 June 2026.
Does this tool change the date for my time zone?
No. The date is treated as a pure calendar day, so every format, including the weekday and the Unix timestamp at midnight UTC, describes the exact same day you picked, with no time-zone shift.
How is the day of the week worked out?
The weekday is derived directly from the calendar date using the Gregorian calendar rules. It depends only on the date, not on your location, so a given date always returns the same day name.
Which date format should I use in a spreadsheet or database?
Use ISO 8601 (YYYY-MM-DD). It sorts in chronological order as text, is never ambiguous, and is the format spreadsheets, databases and APIs parse most reliably. Save the written or slash forms for documents people read.
Is ISO 8601 the same as RFC 3339?
They are closely related. RFC 3339 is a profile of ISO 8601 used in internet standards, so a plain YYYY-MM-DD date works in both. The main difference is that RFC 3339 requires a time zone when a time is included, while ISO 8601 allows the time zone to be left out.
Why does the United States write the month first?
The US month-first order (MM/DD/YYYY) mirrors the way dates are often spoken aloud there, such as "May sixth". Most of the rest of the world writes the day first, which is why converting to ISO 8601 is the reliable way to avoid confusion when data crosses borders.
Sources
- ISO 8601 Date and time format , International Organization for Standardization