Date and time notation in Japan

Date

The most commonly used date format in Japan is "year month day (weekday)", with the Japanese characters meaning "year", "month" and "day" inserted after the numerals. Example: 2008年12月31日 (水) for "Wednesday the 31st of December 2008". The weekday is usually abbreviated to a single character, e.g. 水 for 水曜日 ("Wednesday"), but may also be written in full, then usually without surrounding parenthesis. Apart from the Gregorian calendar, the Japanese Imperial calendar is also used, which bases the year on the current era, which in turn is based on the current emperor. The current era is 平成 Heisei and began in 1989. When using the Imperial calendar, the year is prefixed with the era. For example, the above date using the Imperial calendar is written as: 平成20年12月31日 (水).

Either form may be abbreviated as yy/mm/dd, dots as separators aren't uncommon either. Examples: 20/12/31, 08.12.31. Ambiguities as to which calendar is used for the year are usually only resolved by the context in which the date appears, but Imperial calendar dates may be prefixed with a single letter denoting the era, e.g. 平20/12/31 or H20/12/31. This form is rarely used though and full dates are the preferred way of resolving such ambiguities.

Time

Using the Japanese notation, times are written as "8時42分", with the characters for "hour" and "minute" (optionally also 秒 for "seconds") added after the numerals. It is also common to simply write 8:42 though. Japan uses 24-hour notation, nevertheless 12-hour notation is also often found, using the markers 午前 ("before noon") and 午後 ("after noon"). When using 12-hour notation, both noon and midnight are written as 0, e.g 午後0時15分 or 0:15 for "quarter past noon". The time is usually pronounced as "12:15" or "15 minutes past noon" though.

Times past midnight can also be counted past the 24 hour mark, usually used when the associated activity spans across midnight. For example, bars or clubs may advertise as being open until "26時" (2 a.m.). This form is rarely used colloquially.