A reference for date formats, calendar systems, time zones, and the standards that govern how computers and people record time.
Last reviewed on 25 April 2026.
DDMMYYYY.net is a free, advertising-supported reference covering date and time formats, conversions, calendar systems, time zones, and the libraries developers use to work with all of the above. The goal is straightforward: give a reader a clear, accurate answer to a date or time question without making them piece together fragments from a dozen tabs.
The name comes from the European day-month-year ordering, which sits at the centre of one of the most common sources of date confusion in software and everyday communication. The site treats no single notation as superior — it explains what each format means, where it is used, and when one is preferable to another.
The audience is mixed by design. Developers arrive looking for the right format string in their language of choice, or a clean explanation of why their date arithmetic broke around a daylight saving change. Writers, translators, and analysts arrive trying to make sense of a date a system handed them without context. Students arrive trying to understand why calendars differ in the first place.
The pages are written so that any of those readers can get value without first reading the others. References sit beside short explanations, and explanations link to references when more depth helps.
Content on the site is researched against primary sources where they exist — the relevant ISO and RFC documents for standards, official language documentation for APIs, and the public documentation of the libraries we cover — and against well-established secondary sources for historical and cultural context. Where details are widely accepted but specifics vary by source, we describe the consensus view rather than picking a single number to attach to a name.
We avoid inventing details that cannot be verified. The site does not publish unattributed quotes, fictional case studies, fabricated statistics, or claims that depend on being read in a specific year. When something genuinely changes — a library reaches end of life, a new standard is published, a region adopts or drops daylight saving — the affected pages are revised and their "Last reviewed" date is updated.
Each reference page is structured around a single topic so that internal links make sense without forcing readers through a long chain of pages. Code examples are written to run as shown in current versions of the relevant language or library. Conceptual explanations stay general enough to remain accurate as ecosystems evolve, with version-specific notes called out where they matter.
Pages are reviewed periodically. The review date displayed on each page is the date a human re-read the page end-to-end and confirmed the information, not just a build timestamp. If you spot something that looks out of date or simply wrong, the contact page explains how to get in touch.
DDMMYYYY.net is independent and supported by display advertising, including Google AdSense. Advertising does not influence which standards, libraries, or calendar systems we cover, the recommendations we make, or how we describe trade-offs. The Privacy Policy and Cookie Policy describe how advertising works on the site and what data is involved.