Different conventions exist around the world for date and time
representation, both written and spoken.
2 ISO 8601
3 Local conventions
4 See also
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
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
Which days are considered the weekend.
Main article: ISO 8601
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
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United States (FIPS PUB 4-2 withdrawn in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.
See also: Category:Date and time representation by country
Main article: Date format by country
The little-endian format (day, month, year) is the most popular format
worldwide, followed by the big-endian format (year, month,
day)[better source needed]. Dates may be written partly
in Roman numerals (i.e. the month) or written out
partly or completely in words in the local language.
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
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 and
the Commonwealth, 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, e.g.
"Monday–Friday 6.30–8.30pm". The
BBC website uses the 24-hour
clock for its TV and radio programme listings, while BBC promotions
for upcoming programmes give their times according to the 12-hour
Punctuation and spacing styles differ, even within
English-speaking countries (6:30 p.m., 6:30 pm, 6.30pm,
Most people in "24-hour countries" are so used to both systems being
alternately used in spoken language that they have no problem
switching between the two, perceiving the statements "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
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."). However, encountering a p.m. time written in
the 12-hour notation (e.g. 6:30 meaning 18:30) is likely to cause
confusion with people used to the 24-hour written notation[citation
In certain languages such as Spanish, Portuguese, Dutch, English and
Czech the hour is divided into quarters and halves, spoken of relative
to the closest hour.
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, Dutch
or Swedish 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", in Dutch "half acht" and in Swedish "halv
åtta" invariably means 7:30. For the quarters, in German different
dialects use "Viertel nach sieben" or "viertel acht" (literally
"quarter past seven" or "quarter eight"), and "Viertel vor acht" or
"dreiviertel acht" (literally "quarter to eight" or "three quarters
In the French language, the quarters are expressed as additions or
subtractions of the full hour: "sept heures et quart" (literally
"seven hours and quarter"), "sept heures et demie" ("seven hours and
half"), "huit heures moins le quart" ("eight hours less the quarter").
The separator between hours and minutes is the letter h
(18 h 45, for example).
Common Locale Data Repository, a database that covers national date
and time notations
Date format by country
Date and time notation in Europe