Calendar date

Regnal calendars (that record a date in terms of years since the beginning of the monarch's reign) are also used in some places, for particular purposes.

As such, it is either shorthand for the current year, or else it defines the day of an annual event such as a birthday on 31 May or Christmas on 25 December.

These variations use the sample date of 31 May 2006: (e.g. 31/05/2006, 05/31/2006, 2006/05/31), component separators (e.g. 31.05.2006, 31/05/2006, 31-05-2006), whether leading zeros are included (e.g. 31/5/2006 vs. 31/05/2006), whether all four digits of the year are written (e.g., 31.05.2006 vs. 31.05.06), and whether the month is represented in Arabic or Roman numerals or by name (e.g. 31.05.2006, 31.V.2006 vs. 31 May 2006).

This little-endian sequence is used by a majority of the world and is the preferred form by the United Nations when writing the full date format in official documents.

It is consistent with the big-endianness of the Hindu–Arabic numeral system, which progresses from the highest to the lowest order magnitude.

This form is standard in East Asia, Iran, Lithuania, Hungary, and Sweden; and some other countries to a limited extent.

[4] This date format was commonly used alongside the little-endian form in the United Kingdom until the mid-20th century and can be found in both defunct and modern print media such as the London Gazette and The Times, respectively.

There are several standards that specify date formats: Many numerical forms can create confusion when used in international correspondence, particularly when abbreviating the year to its final two digits, with no context.

The date format of YYYY-MM-DD in ISO 8601, as well as other international standards, have been adopted for many applications for reasons including reducing transnational ambiguity and simplifying machine processing.

[17] This system is most often used in US military logistics since it simplifies the process of calculating estimated shipping and arrival dates.

For example: say a tank engine takes an estimated 35 days to ship by sea from the US to South Korea.

The continuity of representation of period regardless of the time of year being considered is highly useful to both groups of specialists.

[19] Companies in Europe often use year, week number, and day for planning purposes.

In common with most continental European usage, however, all-numeric dates are invariably ordered dd/mm/yyyy.