Date and time representation by country

Date

The little-endian format (day, month, year) is the most popular format worldwide, followed by the big-endian format (year, month, day)^[2]. Dates may be written partly in Roman numerals (i.e. the month) or written out partly or completely in words in the local language.

Time

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 can be 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 clock. Punctuation and spacing styles differ, even within English-speaking countries (6:30 p.m., 6:30 pm, 6.30pm, etc.).

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 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."). 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.

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 eight").

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).