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| <document> | |
| <properties> | |
| <title>Java date and time API - Gregorian calendar system</title> | |
| <author>Stephen Colebourne</author> | |
| </properties> | |
| <body> | |
| <section name="Gregorian calendar system"> | |
| <p> | |
| The Gregorian calendar system is calendar system used by most of the modern business world. | |
| It was first introduced on 1582-10-15 replacing the <a href="cal_julian.html">Julian</a> calendar. | |
| Gregorian rules define a leap year as once every four years, except every 100, but including every 400. | |
| </p> | |
| <p> | |
| The Gregorian chronology in Joda-Time is equivalent* to the ISO chronology, and uses | |
| Gregorian rules for all time. Thus it is not historically accurate before 1583. | |
| This also means that the Gregorian chronology does not correspond to the java class | |
| <code>GregorianCalendar</code>. See <a href="cal_gj.html">GregorianJulian</a> for a | |
| suitable replacement. | |
| </p> | |
| <p> | |
| * The Gregorian and ISO chronologies do in fact differ slightly. | |
| The Gregorian chronology defines a century as it is spoken, | |
| thus 2005 is in the 21st century. | |
| The ISO chronology defines a century as the first two digits of the year, | |
| thus 2005 has a century field of 20. | |
| </p> | |
| <p> | |
| References | |
| <ul> | |
| <li>Calendrical Calculations - Millenium Edition - ISBN 0521777526</li> | |
| <li><a href="http://en.wikipedia.org/wiki/Gregorian_calendar">Wikipedia - Gregorian Calendar</a></li> | |
| </ul> | |
| </p> | |
| </section> | |
| <section name="Using Gregorian chronology in Joda-Time"> | |
| <p> | |
| Within Joda-Time the Gregorian calendar system can be used by obtaining an | |
| instance of <a href="apidocs/org/joda/time/chrono/GregorianChronology.html">GregorianChronology</a>. | |
| This is normally created using the factory method | |
| <a href="apidocs/org/joda/time/chrono/GregorianChronology.html#getInstance()">GregorianChronology.getInstance()</a>. | |
| This is then passed into the constructors of the main date and time classes. | |
| </p> | |
| <source> | |
| // setup date object for midday on Christmas 2004 | |
| Chronology chrono = GregorianChronology.getInstance(); | |
| DateTime dt = new DateTime(2004, 12, 25, 12, 0, 0, 0, chrono); | |
| </source> | |
| </section> | |
| </body> | |
| </document> |