Proleptic

A calendar obtained by extension earlier in time than its invention or implementation is called the "proleptic" version of the calendar.

Algorithm The following pseudocode determines whether a year is a leap year or a common year in the Gregorian calendar (and in the proleptic Gregorian calendar before 1582).

Although these are defined in terms of ISO 8601 which uses the proleptic Gregorian calendar and therefore should include a year 0, the XML Schema specification states that there is no year zero.

Because the Julian calendar was used before that time, one must explicitly state that a given quoted date is based on the proleptic Gregorian calendar if that is the case.

Due to departures from Julius Caesar's intentions, Augustus finished restoring the Julian calendar in March AD 4, and the correspondence between the proleptic Julian calendar and the calendar observed in Rome is uncertain before 8 BC.

Events * 3114 BC According to the proleptic Julian calendar the current era in the Maya Long Count Calendar started.

Other time scales Julian day number is a count of days elapsed since Greenwich mean noon on 1 January 4713 B.C., Julian proleptic calendar.

So the end date is always calculated according to the Gregorian calendar, but the beginning date is usually according to the Julian calendar (or occasionally the Proleptic Gregorian calendar ).

The proleptic Julian calendar uses the Dionysian era throughout, including for dates of Late Antiquity when the Julian calendar was in use but the Dionysian era wasn't, and for times predating the introduction of the Julian calendar.

Thus there is no simple way to find an equivalent in the proleptic Julian calendar of a date quoted using the Roman pre-Julian calendar ( AUC or by reference to consuls ).