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A calendar date is a reference to a particular day represented within a calendar system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "24 " is ten days after "14 " in the Gregorian calendar. The date of a particular event depends on the observed time zone. For example, the air attack on Pearl Harbor that began at 7:48 a.m. Hawaiian time on December 7, 1941, took place at 3:18 a.m. December 8 in Japan (Japan Standard Time). A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: 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 the epoch, with era referring to the particular period of time (Note the different use of the terms in geology). The most widely used epoch is a conventional birthdate of Jesus (which was established by Dionysius Exiguus in the sixth century). A date without the year part may also be referred to as a ''date'' or ''calendar date'' (such as " " rather than " "). As such, it defines the day of an annual event, such as a birthday or Christmas on 24/25 December. Many computer systems internally store points in time in Unix time format or some other system time format. The date (Unix) command—internally using the C date and time functions—can be used to convert that internal representation of a point in time to most of the date representations shown here. ==Date format== There is a large variety of formats for dates in use, which differ in the order of date components (e.g. 31/05/1999, 05/31/1999, 1999/05/31), component separators (e.g. 31.05.1999 vs. 31/05/1999), whether leading zeros are included (e.g. 31/5/1999 vs. 31/05/1999), whether all four digits of the year are written (e.g., 31.05.1999 vs. 31.05.99), and whether the month is represented numerically or by name (e.g. 31 May 1999 vs. 31.05.1999). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Calendar date」の詳細全文を読む スポンサード リンク
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