La fecha es, en el sentido usual, una indicación de tiempo orientada a definir un día único, en general en referencia al calendario gregoriano. La fecha se la utiliza para señalar, junto a la indicación de hora, la existencia o el comienzo o la finalización de un determinado evento temporal. El calendario gregoriano utilizado en nuestros días en la mayor parte de los países europeos y del mundo, se basa en el llamado año terrestre, es decir, el tiempo que tarda el planeta Tierra en dar una vuelta completa alrededor del Sol. El año se divide generalmente en 12 meses, con un total de 365 días (a excepción de los años bisiestos que tienen cada uno 366 días). Los distintos meses tienen cada uno 30 o 31 días, con la excepción de febrero que según sea bisiesto o no, tiene 28 (en el que caso de que no sea bisiesto) o 29 días (en el caso de que lo sea).

Leer el artículo completo en Wikipedia · CC-BY-SA

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 February 2017" is ten days after "14 February 2017" 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 "7 February" rather than "7 February 2017"). 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 timeto most of the date representations shown here.

Leer el artículo completo en Wikipedia · CC-BY-SA