Date and time representation by country
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Differences can exist in:
- The calendar that is used.
- The order in which the year, month and day are represented. (Year-month-day, day-month-year, and month-day-year are the common combinations.)
- How weeks are identified (see seven-day week)
- Whether written months are identified by name, by number (1-12), or by Roman numeral (I-XII).
- Whether the 24-hour clock, 12-hour clock or 6-hour clock is used.
- The punctuation used to separate elements in all-numeric dates and times.
- Which days are considered the weekend.
International standard ISO 8601 (Representation of dates and times) defines unambiguous written all-numeric big-endian formats for dates, such as 1999-12-31 for 31 December 1999, and time, such as 23:59:58 for 23 hours, 59 minutes, and 58 seconds.
These standard notations have been adopted by many countries as a national standard, e.g., BS EN 28601 in the UK and similarly in other EU countries, ANSI INCITS 30-1997 (R2008), and FIPS PUB 4-2 in the United States (FIPS PUB 4-2 withdrawn in United States 2008-09-02). They are, in particular, increasingly widely used in computer applications, since the most to least significant digit order provides a simple method to order and sort time readings.
Many countries use the ISO YYYY-MM-DD date format generally, and they have the advantage of being unambiguous. (YYYY means four-digit year, MM means two-digit month, and DD means two-digit day.) Local conventions can vary, and for the commonly used Gregorian calendar include formats like DD-MM-YYYY, MM-DD-YYYY, YYYY-MM-DD, or even with the month written in Roman numerals. Dates can also be written out partly or completely in words in the local language.
The 24-hour clock enjoys broad everyday usage in most non-English speaking countries, at least when time is written or displayed. In some regions, for example where German, French and Romanian are spoken, the 24-hour clock is used today even when speaking casually, while in other countries the 12-hour clock is used more often in spoken form.
In most English-speaking regions, particularly the United States, the Philippines and the United Kingdom and its former colonies, the 12-hour clock is the predominant form of stating the time with the 24-hour clock used in contexts where unambiguity and accurate timekeeping are important, such as for public transport schedules. Nonetheless, usage is inconsistent: in the UK, train timetables will typically use 24-hour time, but road signs indicating time restrictions (e.g. on bus lanes) typically use 12-hour time.
Most people in "24-hour countries" are so used to both systems that they have no problem switching between the two, perceiving "three o'clock" and "15:00" simply as synonyms. When speaking, a person may often pronounce time in 12-hour notation, even when reading a 24-hour display. It is also common that a person uses the 24-hour clock in spoken language when referring to an exact point in time ("The train leaves at fourteen forty-five …"), while using some variant of the 12-hour notation to refer vaguely to a time ("… so I will be back tonight some time after five.").
In many Germanic languages the half hour is referred to the next hour ("half to nine" rather than "half past eight").
In colloquial language, this can cause confusion between English and German diction: In conversational English as spoken in the UK, "half past eight" (for 8:30) is often reduced to "half eight", while in German "halb acht" is invariably 7:30. For the quarters, in German there is the choice between "viertel nach sieben" or "viertel acht" for "a quarter past seven", and "viertel vor acht" or "dreiviertel acht" for "a quarter to eight".
- Calendar date
- Common Locale Data Repository, a database that covers national date and time notations
- Date format by country