問(wèn)題描述

鑒于公歷開(kāi)始日期是 1582 年 10 月 15 日，請(qǐng)考慮以下測(cè)試并幫助我了解會(huì)發(fā)生什么:

Given that Gregorian Calendar start date is 15 Oct 1582, please consider the following tests and please help me understanding what happens:

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import javax.xml.datatype.DatatypeFactory;
import org.junit.Test;

@Test
public void gregorianToDateConversion() {

    GregorianCalendar calendar = null;
    Date date = null;

    calendar = new GregorianCalendar(1582, 9, 04);
    date = calendar.getTime();
    System.out.println("new GregorianCalendar(1582, 9, 4) -> calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
    System.out.println("calendar.getTime() -> Date:" + date);

    calendar = new GregorianCalendar(1582, 9, 05);
    date = calendar.getTime();
    System.out.println("
new GregorianCalendar(1582, 9, 5) -> calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
    System.out.println("calendar.getTime() -> Date:" + date);

    calendar = new GregorianCalendar(1582, 9, 14);
    date = calendar.getTime();
    System.out.println("
new GregorianCalendar(1582, 9, 14) -> calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
    System.out.println("calendar.getTime() -> Date:" + date);

    calendar = new GregorianCalendar(1582, 9, 15);
    date = calendar.getTime();
    System.out.println("
new GregorianCalendar(1582, 9, 15) -> calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
    System.out.println("calendar.getTime() -> Date:" + date);

    String dateToParse = null;

    dateToParse = "1582-10-04";
    System.out.println("
String to parse: " + dateToParse);
    calendar = parseDateTime(dateToParse);
    if(calendar != null) {
        date = calendar.getTime();
        System.out.println("datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
        System.out.println("calendar.getTime() -> Date: " + date);
    }

    dateToParse = "1582-10-05";
    System.out.println("
String to parse: " + dateToParse);
    calendar = parseDateTime(dateToParse);
    if(calendar != null) {
        date = calendar.getTime();
        System.out.println("datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
        System.out.println("calendar.getTime() -> Date: " + date);
    }

    dateToParse = "1582-10-14";
    System.out.println("
String to parse: " + dateToParse);
    calendar = parseDateTime(dateToParse);
    if(calendar != null) {
        date = calendar.getTime();
        System.out.println("datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
        System.out.println("calendar.getTime() -> Date: " + date);
    }

    dateToParse = "1582-10-15";
    System.out.println("
String to parse: " + dateToParse);
    calendar = parseDateTime(dateToParse);
    if(calendar != null) {
        date = calendar.getTime();
        System.out.println("datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
        System.out.println("calendar.getTime() -> Date: " + date);
    }
}
private GregorianCalendar parseDateTime(String s) {
    DatatypeFactory datatypeFactory = null;
    try {
        datatypeFactory = DatatypeFactory.newInstance();
        return datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar();
    } catch (Exception e) {
        e.printStackTrace();
    } 
    return null;
}

結(jié)果如下:

new GregorianCalendar(1582, 9, 4) -> calendar[DAY_OF_MONTH [4], MONTH [9], YEAR [1582]] **OK**
calendar.getTime() -> Date:Thu Oct 04 00:00:00 CET 1582 **OK**

new GregorianCalendar(1582, 9, 5) -> calendar[DAY_OF_MONTH [15], MONTH [9], YEAR [1582]] **+ 10 days ??**
calendar.getTime() -> Date:Fri Oct 15 00:00:00 CET 1582 **coherent with calendar**

new GregorianCalendar(1582, 9, 14) -> calendar[DAY_OF_MONTH [24], MONTH [9], YEAR [1582]] **+ 10 days ??**
calendar.getTime() -> Date:Sun Oct 24 00:00:00 CET 1582 **coherent with calendar**

new GregorianCalendar(1582, 9, 15) -> calendar[DAY_OF_MONTH [15], MONTH [9], YEAR [1582]] **OK**
calendar.getTime() -> Date:Fri Oct 15 00:00:00 CET 1582 **OK**

String to parse: 1582-10-04
datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH [4], MONTH [9], YEAR [1582]]
calendar.getTime() -> Date: Mon Sep 24 00:00:00 CET 1582 **Not coherent with calendar. Conversion to julian date?**

String to parse: 1582-10-05
datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH [5], MONTH [9], YEAR [1582]]
calendar.getTime() -> Date: Tue Sep 25 00:00:00 CET 1582 **Not coherent with calendar. Conversion to julian date?**

String to parse: 1582-10-14
datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH [14], MONTH [9], YEAR [1582]] **OK**
calendar.getTime() -> Date: Thu Oct 04 00:00:00 CET 1582 **Not coherent with calendar. Conversion to julian date?**

String to parse: 1582-10-15
datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar() -> 
    calendar[DAY_OF_MONTH [15], MONTH [9], YEAR [1582]] **OK**
calendar.getTime() -> Date: Fri Oct 15 00:00:00 CET 1582 **OK**

你能解釋一下發(fā)生了什么嗎?非常感謝.

Could you clarify me what is happening? Thank you very much.

謝謝，我已經(jīng)修正了我在解析日期格式方面的錯(cuò)誤:現(xiàn)在都具有 yyyy-MM-gg 的形式，并且不再拋出異常.

Thank you, I've fixed my mistakes about the format of the date to parse: now all have the form yyyy-MM-gg and no exceptions are thrown anymore.

現(xiàn)在我試著澄清我的疑問(wèn).

Now I try to clarify my dubts.

是什么決定了我們是否使用公歷?
通過(guò)總結(jié):
java.util.GregorianCalendar 表示 1582 年 10 月 15 日之前日期的儒略歷和該日期之后的公歷.對(duì)嗎?
因此，這證明了新 GregorianCalendar(...) 中的行為...
如果我這樣做:

What determines whether or not we are using the proleptic gregorian calendar?
By summarizing:
java.util.GregorianCalendar represents a julian calendar for dates before 15 Oct 1582 and a gregorian calendar after this date. Is it right?
So, this justifies the behaviour in the new GregorianCalendar(...)...
If I do:

new GregorianCalendar(1582, 9, 4) 

我有

calendar[DAY_OF_MONTH [4], MONTH [9], YEAR [1582]]  

因?yàn)?1582 年 10 月 4 日存在于儒略歷中，而我創(chuàng)建的日歷代表儒略日期.
將此日歷轉(zhuǎn)換為日期，我們有:

because 4 Oct 1582 exists in the julian calendar and the calendar I've created represents a julian date.
Converting this calendar to date, we have:

Date:Thu Oct 04 00:00:00 CET 1582, consistent with Calendar.  

如果我這樣做:

new GregorianCalendar(1582, 9, 5)   

我得到

calendar[DAY_OF_MONTH [15], MONTH [9], YEAR [1582]]  

因?yàn)?10 月 5 日在儒略歷和公歷中都不存在.因此 GregorianCalendar 構(gòu)造函數(shù)在 10 月 4 日之后的 1 天創(chuàng)建了一個(gè)日期，即公歷的第一天，即 10 月 15 日.然后用公歷系統(tǒng)表示新日期.
創(chuàng)建一個(gè)從 (1582, 9, 5) 到 (1582, 9, 14) 的新日歷傳遞日期時(shí)，我也會(huì)有同樣的行為.
在上面的例子中，轉(zhuǎn)換后的 java.util.Date 再次與 Calendar 一致

because the day 5 of October neither exists in julian nor in gregorian calendar. So the GregorianCalendar constructor creates a date exactely 1 day after the 4 of October, that is the first day of the gregorian calendar, the 15 of October. The new date is then expressed in gregorian calendar system.
I'll have the same behaviour creating a new calendar passing dates from (1582, 9, 5) to (1582, 9, 14).
In the example above, the converted java.util.Date is again consistent with the Calendar

Date:Fri Oct 15 00:00:00 CET 1582  

如果我這樣做:

new GregorianCalendar(1582, 9, 15)  

我有

calendar[DAY_OF_MONTH [15], MONTH [9], YEAR [1582]]  

因?yàn)?10 月 15 日存在于公歷中，并且新日期在此系統(tǒng)中表示.轉(zhuǎn)換為 Date 的 Calendar 再次保持一致:

because 15 of October exists in gregorian calendar and the new date is expressed in this system. The Calendar converted into Date is again consistent:

Date:Fri Oct 15 00:00:00 CET 1582  

這意味著 GregorianCalendar 構(gòu)造函數(shù)假定我在日歷系統(tǒng)中輸入了在給定紀(jì)元中有效的日期:換句話說(shuō)，假定如果我輸入的日期早于或等于 10 月 4 日，我認(rèn)為日期是根據(jù)到儒略歷并且日期在這個(gè)系統(tǒng)中表示，如果我輸入一個(gè)介于 10 月 5 日到 14 日之間的日期，它會(huì)計(jì)算儒略歷的結(jié)束日期(10 月 4 日)和我輸入的日期之間的天數(shù)，并將這些天數(shù)相加為公歷的開(kāi)始日期(10 月 15 日)并以公歷表示新日期，如果我輸入的日期在 10 月 15 日之后或等于 10 月 15 日，則假定我輸入的日期是公歷，新日期表示為這個(gè)系統(tǒng).
這一切都正確嗎?
這不是一種預(yù)兆行為，對(duì)吧?如果日歷是公歷，我希望用

This means that the GregorianCalendar constructor assumes that I enter dates in the calendar system that is valid in the given epoch: in other words assumes that if I enter a date prior then or equal to 04 October I'm thinking the date according to the julian calendar and the date is expressed in this system, if I enter a date between 05 and 14 October it counts the number of days between the end date of julian calendar (04 october) and the date I entered and sums this days to the start date of gregorian calendar (15 October) and express the new date in gregorian system, and if I enter a date after or equal to 15 October it assumes that the date I entered is meant in gregorian calendar and the new date is expressed in this system.
Is all this correct?
This is not a proleptic behaviour, right? If the calendar was a proleptic gregorian calendar I would expect that initializing it with

new GregorianCalendar(1582, 9, 5)  

我會(huì)得到

calendar[DAY_OF_MONTH [5], MONTH [9], YEAR [1582]]  

如果日期在公歷系統(tǒng)中不存在，也設(shè)置為 10 月 5 日，并且在公歷的第一天之前 10 天，如果我是，它將等于儒略日期 9 月 25 日沒(méi)記錯(cuò).
我如何決定是否使用公歷?

that is the 5 of October is set also if the date does not exists in the gregorian system and, being 10 days befor the first day of gregorian calendar, it would be equal to the julian date 25 september, if I'm not mistaken.
How can I decide to use the proleptic gregorian calendar or not?

解析一個(gè)字符串并通過(guò) XmlGregorianCalendar 創(chuàng)建一個(gè)新的 GregorianCalendar，在我看來(lái)，這種行為有所不同.
解析1582-10-04"我得到

Parsing a String and creating a new GregorianCalendar passing through the XmlGregorianCalendar, the behaviour seems to me different.
Parsing "1582-10-04" I obtain

calendar[DAY_OF_MONTH [4], MONTH [9], YEAR [1582]] 

(和上面的例子一樣)但是一個(gè)日期

(same as the example above..) but a date

Date: Mon Sep 24 00:00:00 CET 1582 

(這里我們有一個(gè)儒略日期，對(duì)嗎?但在上面的例子中(GregorianCalendar 是由它的構(gòu)造函數(shù)創(chuàng)建的)Date 等于 Calendar.為什么現(xiàn)在它不同了?

(Here we have a julian date, is it right? But in the example above (where the GregorianCalendar was created by its constructor) the Date was equal to the Calendar. Why now it is different?

解析我們得到的字符串1582-10-05"

Parsing the string "1582-10-05" we have

calendar[DAY_OF_MONTH [5], MONTH [9], YEAR [1582]] 

(現(xiàn)在我們有了 Proleptic 公歷，對(duì)嗎?)
但又是一個(gè)不同的日期

(Now we have a Proleptic gregorian calendar, right?)
But again a different Date

Date: Tue Sep 25 00:00:00 CET 1582 (Julian Date? Why?)  

解析1582-10-14"的行為相同

Same behaviour parsing "1582-10-14"

calendar[DAY_OF_MONTH [14], MONTH [9], YEAR [1582]]  
Date: Thu Oct 04 00:00:00 CET 1582  

如果我們最終解析1582-10-15"，我們回來(lái)的公歷時(shí)代廣告都變得一致:

If we finally parse "1582-10-15", we come back in the Gregorian age ad all become consistent:

calendar[DAY_OF_MONTH [15], MONTH [9], YEAR [1582]]  
Date: Fri Oct 15 00:00:00 CET 1582  

你能幫我理解所有這些行為嗎?
非常感謝你.

Can you help me to understand all this behaviours?
Thank you very much.

編輯 2:

感謝您的回答，如果我仍有疑問(wèn).我嘗試了以下代碼:

Thank you for your answers, also if some doubt remains for me. I tried the following code:

GregorianCalendar proleptic = new GregorianCalendar();
proleptic.setGregorianChange(new Date(Long.MIN_VALUE));
proleptic.set(Calendar.DAY_OF_MONTH, 5);
proleptic.set(Calendar.MONTH, 9);
proleptic.set(Calendar.YEAR, 1582);
System.out.println("proleptic [DAY_OF_MONTH ["+proleptic.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+proleptic.get(Calendar.MONTH)+"], YEAR ["+proleptic.get(Calendar.YEAR)+"]");
Date prolepticDate = proleptic.getTime();
System.out.println("prolepticDate ["+prolepticDate+"]");

輸出是:

proleptic [DAY_OF_MONTH [5], MONTH [9], YEAR [1582]
prolepticDate [Tue Sep 25 00:24:07 CET 1582]

現(xiàn)在我的日歷 DAY_OF_MONTH 與我設(shè)置的一致，所以我認(rèn)為這是一種預(yù)兆行為，對(duì)吧?但是我再次問(wèn)為什么 getTime() 方法獲得的日期不代表同一天，而是 10 天前.再次感謝.

Now I have the calendar with DAY_OF_MONTH consistent with what I've set, so I think this is a proleptic behaviour, right? But again I ask why the Date, obtained by the getTime() method, does not represent the same day, but 10 days before. Thanks again.

編輯 3:

這個(gè)問(wèn)題對(duì)我來(lái)說(shuō)更清楚一些，但并不完全.我沒(méi)有詳細(xì)理解從 GregorianCalendar 到 Date 的轉(zhuǎn)換是通過(guò)什么邏輯完成的，以及為什么一個(gè)預(yù)測(cè)的公歷和一個(gè)傳統(tǒng)的公歷，每個(gè)都使用與 DAY、MONTH 和 YEAR 相同的參數(shù)構(gòu)造，并不總是代表相同的時(shí)刻.我做了一些進(jìn)一步的測(cè)試.

The question is for me a bit clearer, but not completely. I did not understand in detail by what logic the conversion from GregorianCalendar to Date is done and why a proleptic Gregorian Calendar and a traditional one, each constructed with the same parameters as DAY, MONTH and YEAR, not always represent the same instant of time. I did some further tests.

GregorianCalendar proleptic = null;
GregorianCalendar calendar = null;
Date date = null;

// ---- JULIAN PERIOD ----
proleptic = new GregorianCalendar();
proleptic.clear(); 
proleptic.setGregorianChange(new Date(Long.MIN_VALUE));
proleptic.set(Calendar.DAY_OF_MONTH, 5);
proleptic.set(Calendar.MONTH, Calendar.FEBRUARY);
proleptic.set(Calendar.YEAR, 1582);
System.out.println("proleptic_calendar_5Feb1582 [DAY_OF_MONTH ["+proleptic.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+proleptic.get(Calendar.MONTH)+"], YEAR ["+proleptic.get(Calendar.YEAR)+"]");
date = proleptic.getTime();
System.out.println("date_5Feb1582 from proleptic ["+date+"]");

calendar = new GregorianCalendar(1582, 1, 5);
date = calendar.getTime();
System.out.println("new GregorianCalendar(1582, 1, 5)            -> [DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
System.out.println("new GregorianCalendar(1582, 1, 5) .getTime() -> Date:" + date);

System.out.println("proleptic_calendar_5Feb1582 in millis ["+proleptic.getTimeInMillis()+"], new GregorianCalendar(1582, 1, 5) in millis ["+calendar.getTimeInMillis()+"], millis are equal ["+ (proleptic.getTimeInMillis() == calendar.getTimeInMillis()) +"]");
//--------

System.out.println("
");

// ---- transition period ----
proleptic = new GregorianCalendar();
proleptic.clear(); 
proleptic.setGregorianChange(new Date(Long.MIN_VALUE));
proleptic.set(Calendar.DAY_OF_MONTH, 8);
proleptic.set(Calendar.MONTH, Calendar.OCTOBER);
proleptic.set(Calendar.YEAR, 1582);
System.out.println("proleptic_calendar_8Oct1582 [DAY_OF_MONTH ["+proleptic.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+proleptic.get(Calendar.MONTH)+"], YEAR ["+proleptic.get(Calendar.YEAR)+"]");
date = proleptic.getTime();
System.out.println("date_5Oct1582 from proleptic ["+date+"]");

calendar = new GregorianCalendar(1582, 9, 8);
date = calendar.getTime();
System.out.println("new GregorianCalendar(1582, 9, 8)            -> [DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
System.out.println("new GregorianCalendar(1582, 9, 8) .getTime() -> Date:" + date);

System.out.println("proleptic_calendar_8Oct1582 in millis ["+proleptic.getTimeInMillis()+"], new GregorianCalendar(1582, 9, 8) in millis ["+calendar.getTimeInMillis()+"], millis are equal ["+ (proleptic.getTimeInMillis() == calendar.getTimeInMillis()) +"]");
//--------

System.out.println("
");

// ---- GREGORIAN PERIOD ----
proleptic = new GregorianCalendar();
proleptic.clear(); 
proleptic.setGregorianChange(new Date(Long.MIN_VALUE));
proleptic.set(Calendar.DAY_OF_MONTH, 5);
proleptic.set(Calendar.MONTH, Calendar.DECEMBER);
proleptic.set(Calendar.YEAR, 1582);
System.out.println("proleptic_calendar_5Dec1582 [DAY_OF_MONTH ["+proleptic.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+proleptic.get(Calendar.MONTH)+"], YEAR ["+proleptic.get(Calendar.YEAR)+"]");
date = proleptic.getTime();
System.out.println("date_5Dec1582 from proleptic ["+date+"]");

calendar = new GregorianCalendar(1582, 11, 5);
date = calendar.getTime();
System.out.println("new GregorianCalendar(1582, 11, 5)            -> [DAY_OF_MONTH ["+calendar.get(Calendar.DAY_OF_MONTH)+"], MONTH ["+calendar.get(Calendar.MONTH)+"], YEAR ["+calendar.get(Calendar.YEAR)+"]]");
System.out.println("new GregorianCalendar(1582, 11, 5) .getTime() -> Date:" + date);

System.out.println("proleptic_calendar_5Dec1582 in millis ["+proleptic.getTimeInMillis()+"], new GregorianCalendar(1582, 11, 5) in millis ["+calendar.getTimeInMillis()+"], millis are equal ["+ (proleptic.getTimeInMillis() == calendar.getTimeInMillis()) +"]");
//--------

輸出是:

proleptic_calendar_5Feb1582 [DAY_OF_MONTH [5], MONTH [1], YEAR [1582]
date_5Feb1582 from proleptic [Fri Jan 26 00:00:00 CET 1582]
new GregorianCalendar(1582, 1, 5)            -> [DAY_OF_MONTH [5], MONTH [1], YEAR [1582]]
new GregorianCalendar(1582, 1, 5) .getTime() -> Date:Mon Feb 05 00:00:00 CET 1582
proleptic_calendar_5Feb1582 in millis [-12241069200000], new GregorianCalendar(1582, 1, 5) in millis [-12240205200000], millis are equal [false]

proleptic_calendar_8Oct1582 [DAY_OF_MONTH [8], MONTH [9], YEAR [1582]
date_5Oct1582 from proleptic [Fri Sep 28 00:00:00 CET 1582]
new GregorianCalendar(1582, 9, 8)            -> [DAY_OF_MONTH [18], MONTH [9], YEAR [1582]]
new GregorianCalendar(1582, 9, 8) .getTime() -> Date:Mon Oct 18 00:00:00 CET 1582
proleptic_calendar_8Oct1582 in millis [-12219901200000], new GregorianCalendar(1582, 9, 8) in millis [-12219037200000], millis are equal [false]

proleptic_calendar_5Dec1582 [DAY_OF_MONTH [5], MONTH [11], YEAR [1582]
date_5Dec1582 from proleptic [Sun Dec 05 00:00:00 CET 1582]
new GregorianCalendar(1582, 11, 5)            -> [DAY_OF_MONTH [5], MONTH [11], YEAR [1582]]
new GregorianCalendar(1582, 11, 5) .getTime() -> Date:Sun Dec 05 00:00:00 CET 1582
proleptic_calendar_5Dec1582 in millis [-12214890000000], new GregorianCalendar(1582, 11, 5) in millis [-12214890000000], millis are equal [true]

第一個(gè)測(cè)試(1582 年 2 月 5 日)指的是屬于儒略歷的時(shí)期，第二個(gè)(1582 年 10 月 8 日)屬于過(guò)渡時(shí)期，第三個(gè)(1582 年 12 月 5 日)屬于公歷時(shí)期.然后我覺(jué)得要注意以下幾點(diǎn):

The first test (5 Feb 1582) refers to a period belonging to the Julian calendar, the second (8 Oct 1582) belongs to the period of transition, the third (5 Dec 1582) to the Gregorian Calendar period. Then I think to notice the following things:

儒略時(shí)期

• 預(yù)測(cè)的公歷似乎代表了期望的日期
• 如@Meno Hochschild 所述，獲得的日期被轉(zhuǎn)換為儒略日期(-10 天)
• 傳統(tǒng)的公歷似乎也代表了希望的日期...
• 但是獲取到的Date和之前的不一樣
• 其實(shí)，兩個(gè)公歷代表兩個(gè)不同的時(shí)間瞬間，看毫秒值

過(guò)渡期

• 預(yù)測(cè)的公歷似乎代表了期望的日期
• 再次將獲得的日期轉(zhuǎn)換為儒略日期(-10 天)
• 傳統(tǒng)的公歷似乎是公歷轉(zhuǎn)換的結(jié)果(10 月 8 日)，最初以預(yù)測(cè)儒略歷表示(10 月 8 日 = 4 天，然后儒略歷 MAX DATE(10 月 4 日)= 3比公歷多天 MIN DATE = 15 + 3 = 10 月 18 日(這是一個(gè)假設(shè))
• 這次獲取的Date好像代表了上面?zhèn)鹘y(tǒng)公歷的同一個(gè)日期(這次沒(méi)有轉(zhuǎn)換為儒略日?)
• 兩個(gè)公歷再次代表兩個(gè)不同的時(shí)刻，查看毫秒值

公歷

• 預(yù)測(cè)的公歷代表期望的日期
• 獲取的Date代表相同的日期
• 傳統(tǒng)的公歷代表所需的日期
• 獲取的Date代表相同的日期
• 兩個(gè)公歷代表同一時(shí)刻，同一毫秒數(shù)

你能幫我一一解釋所有這些結(jié)果嗎?

Could you help me to explain one by one all of these results?

謝謝.

推薦答案

方法 newXMLGregorianCalendar(s) 必須輸入格式為yyyy-MM-dd"的字符串，即使用 兩位數(shù)表示月份中的某天.但是您已經(jīng)定義了字符串1582-10-4"和1582-10-5"(而不是1582-10-04"和1582-10-05").

Method newXMLGregorianCalendar(s) must be feeded with a string in format "yyyy-MM-dd", that is using TWO digits for the day of month. But you have defined the strings "1582-10-4" and "1582-10-5" (instead of "1582-10-04" and "1582-10-05").

我已經(jīng)測(cè)試了替代品，它可以工作.

I have tested the replacement, and it works.

請(qǐng)記住，XMLGregorianCalendar 非常嚴(yán)格，并且還根據(jù) ISO-8601 中的標(biāo)準(zhǔn)約定使用預(yù)測(cè)公歷.這意味著，它甚至在 1582 年之前就使用公歷閏年規(guī)則.這解釋了您的陳述與日歷不一致.轉(zhuǎn)換為儒略日期?".例如:

Remember that XMLGregorianCalendar is very strict and also uses the proleptic gregorian calendar according to the standard convention in ISO-8601. That means, it uses the gregorian leap year rules even before 1582. This explains your statement "Not coherent with calendar. Conversion to julian date?". For example:

教皇在日期 1582-10-04(舊儒略歷)之后的 10 天撤職，因此在此之后，日期 1582-10-15 在新公歷中緊隨其后.在公歷中，日期 1582-10-14 定義明確，對(duì)應(yīng)于 1582-10-15 的前一天，因此(歷史儒略)日期為 1582-10-04.

The pope had removed 10 days following the date 1582-10-04 (in old julian calendar), so after this the date 1582-10-15 immediately followed in new gregorian calendar. In the proleptic gregorian calendar the date 1582-10-14 is well defined and corresponds to one day before 1582-10-15, hence the (historic julian) date 1582-10-04.

OP 編輯??后更新:

您的問(wèn)題是什么決定了我們是否使用公歷?"的簡(jiǎn)單答案是:你決定.

The simple answer to your question "What determines whether or not we are using the proleptic gregorian calendar?" is: You decide.

詳細(xì)說(shuō)明:如果您使用 XMLGregorianCalendar，那么您使用的是公歷.

In detail: If you use XMLGregorianCalendar then you use the proleptic gregorian calendar.

如果你使用 java.util.GregorianCalendar 那么你默認(rèn)選擇了日期 1582-10-15 作為公歷的第一天.所有過(guò)去的日子都被認(rèn)為是在儒略歷中.但是，您可以覆蓋默認(rèn)切換日期.為此，您只需調(diào)用方法 setGregorianChange(Date) 帶有適當(dāng)?shù)膮?shù).new Date(Long.MIN_VALUE) 的參數(shù)設(shè)置預(yù)測(cè)公歷，而 new Date(Long.MAX_VALUE) 的參數(shù)設(shè)置預(yù)測(cè)儒略歷.

If you use java.util.GregorianCalendar then you have choosen the date 1582-10-15 as the first day of gregorian calendar by default. All former days are considered as being in julian calendar. You can override the default switch date however. For this to make work you just call the method setGregorianChange(Date) with an appropriate argument. An argument of new Date(Long.MIN_VALUE) sets the proleptic gregorian calendar while an argument of new Date(Long.MAX_VALUE) sets the proleptic julian calendar.

同樣重要的是要注意

a) 大多數(shù)國(guó)家在 1582 年 10 月 15 日沒(méi)有改用公歷(只有主要的天主教國(guó)家)，

a) most countries did not switch to gregorian calendar in 1582-10-15 (only major catholic countries),

b) 歷史日期由其他因素進(jìn)一步確定，例如不同的年初(這使得 JDK 中的整個(gè) julian-gregorian-calendar-implementation 完全不足 - 目前沒(méi)有提供支持的庫(kù)).

b) historical dates are further determined by other factors like different start of year (which makes the whole julian-gregorian-calendar-implementation in JDK completely insufficient - currently there is no library which gives support).

EDIT-2 后更新:

輸出 proleptic [DAY_OF_MONTH [5], MONTH [9], YEAR [1582] 符合預(yù)期，并保留了 proleptic 公歷中定義的輸入(1582-10-15 前 10 天)向后應(yīng)用公歷閏年規(guī)則).

The output proleptic [DAY_OF_MONTH [5], MONTH [9], YEAR [1582] is as expected and conserves the input as defined in proleptic gregorian calendar (10 days before 1582-10-15 applying the gregorian leap year rules backwards).

輸出 prolepticDate [Tue Sep 25 00:24:07 CET 1582] 是一個(gè)完全不同的故事.但是如果您記得您確實(shí)在 java.util.Date 上調(diào)用了方法 toString()，那就可以理解了.此方法在內(nèi)部實(shí)例化一個(gè)新的公歷對(duì)象，默認(rèn)開(kāi)關(guān)為 1582-10-15. Date-對(duì)象不知道(也沒(méi)有內(nèi)部狀態(tài))設(shè)置公歷更改的日期，因此它的 toString() 方法只應(yīng)用默認(rèn)值.最后，預(yù)測(cè)日歷對(duì)象只是重新計(jì)算/重新格式化為 Date.toString() 特定格式的儒略歷表示.即:1582-09-25(切換前十天).

The output prolepticDate [Tue Sep 25 00:24:07 CET 1582] is a completely different story. But it is understandable if you remember that you really called the method toString() on java.util.Date. This method internally instantiates a new gregorian calendar object with the default switch of 1582-10-15. A Date-object has no idea (and no internal state) about setting the date for gregorian change, so its toString()-method just applies the default. Finally the proleptic calendar object is just recalculated/reformatted to a julian calendar representation in the specific format of Date.toString(). That is: 1582-09-25 (ten days before the switch).

由于@VGR 的評(píng)論而更新:

我的測(cè)試驗(yàn)證，例如對(duì)于預(yù)測(cè)日期 1582-10-05，XMLGregorianCalendar 和新 GregorianCalendar 的專門(mén)構(gòu)造自 unix 以來(lái)以毫秒為單位產(chǎn)生相同的時(shí)間-epoch，見(jiàn)這里:

My test verifies that for example for the proleptic date 1582-10-05 both XMLGregorianCalendar and a specialized construction of a new GregorianCalendar yield the same time in millis since unix-epoch, see here:

String s = "1582-10-05";
DatatypeFactory datatypeFactory = DatatypeFactory.newInstance();
GregorianCalendar xml = datatypeFactory.newXMLGregorianCalendar(s).toGregorianCalendar();

GregorianCalendar proleptic = new GregorianCalendar();
proleptic.clear(); // very important for proper comparison to reset time part to zero
proleptic.setGregorianChange(new Date(Long.MIN_VALUE));
proleptic.set(Calendar.DAY_OF_MONTH, 5);
proleptic.set(Calendar.MONTH, Calendar.OCTOBER);
proleptic.set(Calendar.YEAR, 1582);

boolean isEqual = (xml.getTimeInMillis() == proleptic.getTimeInMillis());

System.out.println("XML-millisSinceEpoch: " + xml.getTimeInMillis());
System.out.println("Proleptic-millisSinceEpoch: " + proleptic.getTimeInMillis());
System.out.println("XML==Proleptic (1582-10-05): " + isEqual);
System.out.println(
    "proleptic [DAY_OF_MONTH [" + proleptic.get(Calendar.DAY_OF_MONTH) + "], MONTH ["
    + proleptic.get(Calendar.MONTH) + "], YEAR [" + proleptic.get(Calendar.YEAR) + "]"
);
System.out.println("Date.toString() [" + proleptic.getTime() + "]");

輸出:

XML-millisSinceEpoch: -12220160400000
Proleptic-millisSinceEpoch: -12220160400000
XML==Proleptic (1582-10-05): true
proleptic [DAY_OF_MONTH [5], MONTH [9], YEAR [1582]
Date.toString() [Tue Sep 25 00:00:00 CET 1582]

這篇關(guān)于1582 年 10 月 15 日之前日期的日歷到日期轉(zhuǎn)換.公歷到儒略歷切換的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！