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gce# Gregorian Common Era

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Calendar Description

This version of the Gregorian calendar is occasionally used when referring to dates in the first millennium and earlier, similar to the Julian Common Era scheme. The calendar is split into two eras, the Common Era (also known as the Christian Era or AD - Anno Domini) and Before Common Era (also known as Before Christian Era or BC - Before Christ).

Dates Before Common Era end on the 31st December year 1 BCE and the years are counted backwards from this point for all previous years. The Common Era start the next day, the 1st January, year 1 CE and continues until the present day. Thus, years are always positive and there is no year zero. Leap years follow the same rules as the Gregorian calendar scheme.

Use Case

For dates in the Common Era this scheme is the same as the Gregorian scheme, which includes the period for when it was in contemporary use. As this scheme requires an additional field (BCE or CE), the simpler Gregorian scheme is preferred. However, when dealing with dates before the second millennium it is convenient for Historians to use a single scheme.

Definition

Record - Default order
yearmonthdaywdayceceyear
Record - Ranking order
ceceyearmonthdaywdayyear

The Gregorian Common Era scheme is a variation of the Gregorian scheme and has the same definition except that it includes the optional fields ce and ceyear.

The Record consists of three Fields named year, month and day and the optional Field wday - these are as described for the Gregorian scheme. As stated, the record also includes the optional Fields ce and ceyear. These fields are ranked into the order shown in the Record.

The ce field has the value 0 for all values of year less than one, and the value 1 for all other values of year.

The ceyear field has the value -year + 1 for all values of year less than one, and the value year for all other values.

The Epoch is set at
gcececeyearmonthday
1111
=
jcececeyearmonthday
1113
=
jdnday
1721426
.

Script

Default Script
scheme gce { name "Gregorian Common Era"; base gregorian; grammar jce; }

The script makes use of the grammar jce which is described in the Julian Common Era scheme.


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11th August 2015