Date Formatting Standardization
By Don Hillger, SU-5200

There has been discussion in our newsletter Astrophile during the past year about date notation, and the possibility of confusion when dates are written in all numeric form. For example, is the date 1/4/2000 actually January 4 or April 1?

In the United States (except for military usage) it is common to write dates in the mm/dd/yyyy format. This date format follows from our tradition of saying the date with the month first, such as January 4, 2000, which is abbreviated numerically as 1/4/2000. However, in most non-U.S. usage the day is given first, as 4 January 2000, resulting in the all-numeric form 4/1/2000 (the most common date format in the world).

As a group with members from many countries, how do we avoid confusion between these dating systems? One way is to always spell out the month, but most of us do not do that in our stamp records/databases. (You'll note that Scott catalogs spell out the month, and they do not use the mm/dd/yyyy format!) Astrophile has not required dates to be in a consistent format. In lieu of adopting a standard format they list the date format along with each usage, so that the convention is known for each article. However this still requires members in different countries to convert back and forth between date formats.

The Date Formatting Solution

The real solution is to follow the internationally-recommended date format, which has the year first, yyyy/mm/dd (or yyyy-mm-dd, with hyphens instead of forward slashes). This standard format was devised to avoid the very problem we are encountering. The International Organization for Standardization (ISO) standard is ISO-8601 which can be found at the website listed at the end of this article. In this standard format the year is followed by the month, then by the day. The descending-numerical-significance of the components is more logical, like our counting system with thousands, then hundreds, then tens, then single digits. This makes a lot more sense than putting the day, which changes the fastest, between the month and the year. Even the non-U.S. format is more logical than the U.S. form, since the components are in order of ascending-numerical-significance, a reverse of the ISO format.

With the year first, both date formats in common usage, the U.S. form and the non-U.S. form, will change. The more-logical year-first format is easier to understand and easier to sort. The Canadian government has chosen this international date format for their official business (but most Canadians still use the U.S. date format)

Of course, this discussion assumes that a 4-digit year is used. Otherwise, there is room for additional confusion if the year can be confused with either the month or the day. For the years 2001 thru 2012 a 2-digit year can be confused with both the month and the day. For example, what does the date 01/02/03 represent in all possible formats? Using 4-digit years at least solves that part of the problem! Y2K did that much for us.

For further information on date formatting see the following useful websites:

A Summary of the International Standard Date and Time Notation, by Markus Kuhn

Campaign to get the Internet World to use the International Date Format, by Steve Adams (

International Organization for Standardization (ISO) standard ISO-8601

So, what will you do?

The rest of the world is not going to start using the U.S. date format (just as the world is not going to abandon the metric system). Rather it's up to people like us to use a more logical date format system, one that is internationally understood and cannot be misunderstood. Leave it to the isolationists and the protectionists to stick with their favorite date format and let us be the pioneers! Start using the ISO (international) date format in your stamp records/databases, and especially in the articles you publish!

(Note from WebMaster: I'll change the dates on our Web site to year-month-day as I modify pages, although I'll usually spell out the month) RJS.)

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