A calendar is simply a coordinate system of marking days. This is usually done by giving individual titles to days of weeks, months, days and years normally. A date is the shortest designation of a given month or day in such a coordinate system. A calendar, in essence, is just a physical recording of such an coordinate system. When you download Android calendar app to your phone you are essentially doing the same thing.
The calendar, in the main article above, was used in the Early Modern period (the calendar was established in the thirteenth century), but the underlying idea has been around much longer than that. It actually comes to us from the Palaces of the Renaissance. It is interesting to note that the name of the calendar in it's modern form came from Latin - "calendula", which can be translated as handkerchief. The original meaning of the word was a cloth, hence, "books of handkerchiefs".
The earliest kind of calendar was a lunisolar calendar, a calendar worked out in a lunisolar year. Each individual country's solar year was assigned a name and a month. This was a great piece of software to have, because it gave each nation a distinct identity. When you looked at the moon, each quarter had a different name and a different month. This was a very helpful way for early modern man to track his sheep and to know when they were laying eggs. You can download Android calendar app to your phone today, but do remember that this program does not work on the new version of Android - it only works on the Gingerbread version.
