An internationally accepted way to represent dates and times using numbers.

When dates are represented with numbers they can be interpreted in different ways. For example, 01/05/12 could mean January 5, 2012, or May 1, 2012. On an individual level this uncertainty can be very frustrating, in a business context it can be very expensive. Organizing meetings and deliveries, writing contracts and buying airplane tickets can be very difficult when the date is unclear.

ISO 8601 tackles this uncertainty by setting out an internationally agreed way to represent dates:


For example, September 27, 2012 is represented as 2012-09-27.

Preview our standards

ISO 8601-1:2019

ISO 8601-2:2019

What can ISO 8601 do for me?

ISO 8601 can be used by anyone who wants to use a standardized way of presenting dates and times. It helps cut out the uncertainty and confusion when communicating internationally.

The full standard covers ways to write:

  • Date
  • Time of day
  • Coordinated universal time (UTC)
  • Local time with offset to UTC
  • Date and time
  • Time intervals
  • Recurring time intervals

How can I get ISO 8601?

You can buy the full standard from the ISO Store, or from the ISO member in your country.

ISO Store

Visit the ISO Store to buy more standards

Useful articles

Date and time: the new draft of ISO 8601 explained by Klaus-Dieter Naujok
Standardization is a truly international activity, and I've been lucky to have worked with more nationalities than I can remember. But, that said, my first business meeting with a German remains etched …