When writing procedures related to history or calendar, the Gregoriancalendar class provided by JDK is very easy. It can reproduce the August Corgeted Confucius calendar and 1582 Pope regraph the GEL highlightener, namely October 4, 1582, in accordance with the Confucian calendar rules, after 15 October 1582, it will be handled in Glieli, and the 10 days of the Glue Gaoli can also handle it (even for Western Europe). All countries have changed the success, and they set different reform times Gregoriancalendar.SetgregorianChange ()).
However, the Gregoriancalendar class still has its applicable range, which cannot reflect the problem of calendar chaos that occurred in the ancient Roman calendar, 45 years to the 4th year of BC (these 49 years old Roman calendar is far from being perfect, and the historical material is insufficient, The actual calendar calendar is difficult to test, and the results of the future generations also have different differences). For example, in accordance with the most common opinion in the historiographic boundaries, the 4 years of Rome, Rome, is still 28 days in February this year. But we used the Gregoriancalendar class to calculate, there were 29 days in February 4 years.
How to deal with this problem depends on your attention. If you just want to calibrate the past event with a passable time scale, you can use the GregorianCalendar class to any year. In fact, when the research object is not related to human history or human society, it is also a variety of calendar differences in 1582 (main differences in changing the way in the past 100 years). However, if you care about the ancient Rome or the relevant historical events, or you want the Calendum of Rome as the reference system, you must introduce the correction code for the GregorianCalendar class. Of course, how to fix it, this will also depend on your specific opinions on the ancient Roman calendar. If you believe in ancient Rome in 4 years, you agree to the future generations, and so on.
Below is the relevant interpretation in the JDK 1.4 document:
However, dates obtained using GregorianCalendar are historically accurate only from March 1, 4 AD onward, when modern Julian calendar rules were adopted. Before this date, leap year rules were applied irregularly, and before 45 BC the Julian calendar did not even exist.
Below is a different opinions from the academic circles to 45 years from 45 years to AD, the leap year set up chaos:
The historic sequence of leap years (ie years with a leap day) in this period is not given explicitly by any ancient source, although the existence of the triennial cycle is confirmed by an inscription that dates from 9 or 8 BC. The chronologist Joseph Scaliger Established in 1583 That The Augustan Reform Was Institutions IN 8 BC, AND INFERRED That SEQUENCE OF LEAP YEARS WAS 42 BC, 39 BC, 36 BC, 33 BC, 30 BC, 27 BC, 24 BC, 21 BC, 18 BC, 15 BC, 12 BC, 9 BC, AD 8, AD 12 etc. This proposal is still the most widely accepted solution. Other solutions have been proposed from time to time. Kepler proposed in 1614 that the correct sequence of leap years was 43 BC, 40 BC, 37 BC, 34 BC, 31 BC, 28 BC, 25 BC, 22 BC, 19 BC, 16 BC, 13 BC, 10 BC, AD 8, AD 12 etc. in 1883 The German Chronologist Matzat proposed 44 BC, 41 BC, 38 BC, 35 BC, 32 BC, 29 BC, 26 BC, 23 BC, 20 BC, 17 BC, 14 BC, 11 BC, AD 4, AD 8, AD 12 etc., Based ON A Passage In Dio Cassius That Mentions a Leap Day in 41 BC That Was Said to be contrary to Caesar's rule. It has also sometimes been suggested that 45 BC was a leap year. In the 1960s Radke argued the reform was actually instituted when Augustus became pontifex maximus in 12 BC, suggesting the sequence 45 BC, 42 BC, 39 BC, 36 BC, 33 BC, 30 BC, 27 BC, 24 BC, 21 BC, 18 BC, 15 BC, 12 BC, AD 4, AD 8, AD 12 etc.in 1999, An Egyptian PAPYRUS WAS PUBLISHED GIVES AN Ephemeris Table for 24 BC with Both Roman and Egyptian Dates. from this it can be shown That The MOST LIKELY SEQUENCE WAS in Fact 44 BC, 41 BC, 38 BC, 35 BC, 32 BC, 29 BC, 26 BC, 23 BC, 20 BC, 17 BC, 14 BC, 11 BC, 8 BC, AD 4, AD 8, AD12 etc., Very Close to That proposed by matzat.