Date Format Converter — DD/MM/YYYY, ISO, Julian Day
Convert any date to all formats: DD/MM/YYYY, MM/DD/YYYY, YYYY-MM-DD, day of week, and Julian day number.
Date Format Guide
| Format | Example | Used In |
|---|---|---|
| DD/MM/YYYY | 16/03/2025 | Nigeria, UK, Europe, most of the world |
| MM/DD/YYYY | 03/16/2025 | United States only |
| YYYY-MM-DD | 2025-03-16 | ISO 8601 — international standard |
| D MMMM YYYY | 16 March 2025 | Formal documents, letters |
| MMMM D, YYYY | March 16, 2025 | US formal documents |
| DD-MMM-YYYY | 16-Mar-2025 | Aviation, military, banking |
Frequently Asked Questions
What is the ISO 8601 date format?
ISO 8601 is the international standard: YYYY-MM-DD (e.g., 2025-03-16). It is unambiguous, sorts correctly alphabetically, and is used in computing, databases, and international communication.
What is the Julian Day Number?
The Julian Day Number (JDN) is a continuous count of days since January 1, 4713 BC (Julian calendar). It is used in astronomy and chronology. For example, January 1, 2000 = JDN 2,451,545.
What is the difference between DD/MM/YYYY and MM/DD/YYYY?
DD/MM/YYYY (day first) is used in Nigeria, UK, Europe, and most of the world. MM/DD/YYYY (month first) is used in the United States. Confusion between these formats causes errors in international documents.
What day of the week is used in Nigeria officially?
The week in Nigeria officially starts on Monday. However, most calendar apps show Sunday as the first day. The standard ISO week numbering also starts on Monday.
How do I find what day of the week a date falls on?
Enter any date in this tool to instantly see what day of the week it falls on. You can also use the Zeller formula or Tomohiko Sakamoto's algorithm for manual calculation.