Calendar date
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A date in a calendar is a reference to a particular day by means of a calendar system. The calendar date allows the particular day to be identified. A person can often determine how many days a particular date comes after another date. For example, "February 19, 2003", is ten days after "February 9, 2003", in the Gregorian calendar.
In most calendar systems, the date consists of three parts: the , the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called an era, but sometimes an epoch.
A date without the year part may also be referred to as a date or calendar date (such as "9 February" rather than "9 February 2003"). As such, it defines the days of an annual festival, such as a birthday or Christmas on 25 December.
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Date format
Related to the classification of a day as a specific calendar date is the format used to express that date.
Even for any specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar:
Forms starting with the day
This sequence is common to the vast majority of the world's countries, and is used as the accepted international date usage.
- 16/11/2001, 16.11.2001, 16-11-2001 or 16-11-01
- 16th of November 2001
- 16th November 2001
- 16 November 2001
- 16 Nov 2001
Forms starting with the year
- 2001 November 16
- 2001-11-16: the ISO 8601 International formal standard ordering for dates, often formatted to be especially easily read and sorted by computers. It's used with UTC in the Internet date/time format (see the external link below). This format is also favored in certain Asian countries, mainly the East Asia.
Forms starting with the month
This sequence is common to a smaller number of countries.
- November 16, 2001
- Nov. 16, 2001
- 11/16/2001, 11-16-2001, 11.16.2001 or 11.16.01
This order is used in the United States and countries with U.S. influence (but the U.S. federal government sometimes uses day, month, year). England originally used day, month, year, then for a while used month, day, year, and finally the original form (day, month, year) was revived around 1900. Canada uses both conventions, those starting with the day and those starting with the month.
Usage issues
The many numerical forms can create confusion when used in international correspondence, particularly when abbreviating the year to its final two digits.
When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". Many Internet sites use year/month/day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, etc.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous.
The ISO 8601 standard also has the advantage of being language independent and therefore is useful when there may be no language context and a universal application is desired (expiration dating on export products, for example).
At least in the United States, dates are rarely written in purely numerical forms in formal writing.
Also, some people say that the order starting with the month is illogical, because it does not indicate the units in order of size, either increasing or decreasing.
The differing formats of dates are an example of endianness.
(day, month, year) is used by:
- Albania
- Argentina
- Australia
- Austria
- Belgium
- Bolivia
- Brazil
- Bulgaria
- Canada
- Chile
- Colombia
- Czech Republic
- Denmark (often in the fraction form d/m-y)
- Ecuador
- Estonia
- Finland
- France
- Germany
- Great Britain
- Guyana
- Hong Kong (in English)
- Hungary
- Ireland
- India
- Italy
- Lithuania
- Mexico
- Netherlands
- New Zealand
- Norway (in the fraction form d/m-y)
- Paraguay
- Peru
- Poland
- Portugal
- Romania
- Russia
- Slovakia
- Slovenia
- Spain
- Singapore
- Sweden (in the fraction form d/m-y)
- Switzerland
- Turkey
- Uruguay
- Venezuela
y/m/d (year, month, day), the ISO 8601 standard, is used by:
m/d/y (month, day, year) is used by:
- Canada (Although most offical documents use the d/m/y format, the m/d/y format is also understood)
- United States
Day and year only
The U.S. military sometimes uses a system that indicates the year and day, but not the month. For example, "December 10, 1999" can be written in some contexts as "9345", for the 345th day of 1999. This system is most often used on forms.
- See also: calendar, time, date-time group, Japanese calendar, Wikibooks:English:Time
External links
- Date calculator, add or subtract days to or from a given date (http://www.timeanddate.com/date/dateadd.html).
- IETF:RFC 3339 (http://www.ietf.org/rfc/rfc3339.txt), Internet date/time format.
- English Dates (http://www.ego4u.com/en/cram-up/vocabulary/date) - explanations, exercises and date generator (written and spoken dates)de:Datumsformat