blocks|key|1498728|text|int+x+=+-1;
Calendar+cal+=+...;
cal.add(Calendar.DATE,+x);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1498729|请参阅java.util.Calendar#add(int,int)|unstyled|offset|length|style|CODE|1498730|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/10/docs/api/java/util/Calendar.html#add(int,int)^0|0|3|V|3|V|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|T|8|@$G|U|H|V|I|J]]|9|@$G|W|H|X|1|Y]]|A|$]]|$1|K|3|-4|5|F|7|Z|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

<pre><code>int x = -1;
Calendar cal = ...;
cal.add(Calendar.DATE, x);
</code></pre>
See <a href="https://docs.oracle.com/javase/10/docs/api/java/util/Calendar.html#add(int,int)" rel="nofollow noreferrer"><code>java.util.Calendar#add(int,int)</code></a>

blocks|key|1498746|text|您可以使用add方法并向其传递一个负数。但是，您也可以编写一个不使用Calendar类的更简单的方法，如下所示|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1498747|public+static+void+addDays(Date+d,+int+days)
{
++++d.setTime(+d.getTime()+%2B+(long)days*1000*60*60*24+);
}|code-block|syntax|javascript|1498748|这将获取日期的时间戳值(从纪元开始的毫秒数)，并添加适当的毫秒数。您可以为days参数传递一个负整数来进行减法。这将比“适当的”日历解决方案更简单：|1498749|public+static+void+addDays(Date+d,+int+days)
{
++++Calendar+c+=+Calendar.getInstance();
++++c.setTime(d);
++++c.add(Calendar.DATE,+days);
++++d.setTime(+c.getTime().getTime()+);
}|1498750|请注意，这两种解决方案都会更改作为参数传递的Date对象，而不是返回一个全新的Date。如果需要，这两个函数都可以很容易地更改为另一种方式。|1498751|entityMap^0|5|3|Y|8|0|0|0|0|M|4|13|4|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|R|$]]

You could use the <code>add</code> method and pass it a negative number. However, you could also write a simpler method that doesn't use the <code>Calendar</code> class such as the following

<pre><code>public static void addDays(Date d, int days)
{
 d.setTime( d.getTime() + (long)days*1000*60*60*24 );
}
</code></pre>

This gets the timestamp value of the date (milliseconds since the epoch) and adds the proper number of milliseconds. You could pass a negative integer for the days parameter to do subtraction. This would be simpler than the "proper" calendar solution:

<pre><code>public static void addDays(Date d, int days)
{
 Calendar c = Calendar.getInstance();
 c.setTime(d);
 c.add(Calendar.DATE, days);
 d.setTime( c.getTime().getTime() );
}
</code></pre>

Note that both of these solutions change the <code>Date</code> object passed as a parameter rather than returning a completely new <code>Date</code>. Either function could be easily changed to do it the other way if desired.

blocks|key|1498779|text|对于简单的情况，Anson's+answer可以很好地工作，但如果您要进行更复杂的日期计算，我建议您查看Joda+Time。它会让你的生活变得更轻松。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1498780|仅供参考，在Joda时间你可以做|1498781|DateTime+dt+=+new+DateTime();
DateTime+fiveDaysEarlier+=+dt.minusDays(5);|code-block|syntax|javascript|1498782|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/212321/anyone-know-a-simple-way-using-java-calendar-to-subtract-x-days-to-a-date#212334|1|http://joda-time.sourceforge.net/^0|8|E|0|1G|9|1|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]|$A|Y|B|Z|1|10]]|C|$]]|$1|D|3|E|5|6|7|11|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|12|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

<a href="https://stackoverflow.com/questions/212321/anyone-know-a-simple-way-using-java-calendar-to-subtract-x-days-to-a-date#212334">Anson's answer</a> will work fine for the simple case, but if you're going to do any more complex date calculations I'd recommend checking out <a href="http://joda-time.sourceforge.net/" rel="nofollow noreferrer">Joda Time</a>. It will make your life much easier.

FYI in Joda Time you could do

<pre><code>DateTime dt = new DateTime();
DateTime fiveDaysEarlier = dt.minusDays(5);
</code></pre>

blocks|key|1713885|text|Eli+Courtwright的第二个解决方案是错误的，它应该是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1713886|Calendar+c+=+Calendar.getInstance();
c.setTime(date);
c.add(Calendar.DATE,+-days);
date.setTime(c.getTime().getTime());|code-block|syntax|javascript|1713887|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Eli Courtwright second solution is wrong, it should be:

<pre><code>Calendar c = Calendar.getInstance();
c.setTime(date);
c.add(Calendar.DATE, -days);
date.setTime(c.getTime().getTime());
</code></pre>

blocks|key|1713908|text|这可以通过以下方式轻松完成|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1713909|Calendar+calendar+=+Calendar.getInstance();
++++++++//+from+current+time
++++++++long+curTimeInMills+=+new+Date().getTime();
++++++++long+timeInMills+=+curTimeInMills+-+5+*+(24*60*60*1000);++++//+`enter+code+here`subtract+like+5+days
++++++++calendar.setTimeInMillis(timeInMills);
++++++++System.out.println(calendar.getTime());

++++++++//+from+specific+time+like+(08+05+2015)
++++++++calendar.set(Calendar.DAY_OF_MONTH,+8);
++++++++calendar.set(Calendar.MONTH,+(5-1));
++++++++calendar.set(Calendar.YEAR,+2015);
++++++++timeInMills+=+calendar.getTimeInMillis()+-+5+*+(24*60*60*1000);
++++++++calendar.setTimeInMillis(timeInMills);
++++++++System.out.println(calendar.getTime());|code-block|syntax|javascript|1713910|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

It can be done easily by the following

<pre><code>Calendar calendar = Calendar.getInstance();
 // from current time
 long curTimeInMills = new Date().getTime();
 long timeInMills = curTimeInMills - 5 * (24*60*60*1000); // `enter code here`subtract like 5 days
 calendar.setTimeInMillis(timeInMills);
 System.out.println(calendar.getTime());

 // from specific time like (08 05 2015)
 calendar.set(Calendar.DAY_OF_MONTH, 8);
 calendar.set(Calendar.MONTH, (5-1));
 calendar.set(Calendar.YEAR, 2015);
 timeInMills = calendar.getTimeInMillis() - 5 * (24*60*60*1000);
 calendar.setTimeInMillis(timeInMills);
 System.out.println(calendar.getTime());
</code></pre>

blocks|key|1498896|text|我面临着同样的挑战，我需要返回1天(即使前一天是前一年或前几个月，也应该能够回滚到前一天)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1498897|我做了以下，基本上减去24小时为1天。someDateInGregorianCalendar.add(Calendar.HOUR，-24)；|1498898|或者，我也可以这样做|1498899|GregorianCalendar+cal+=+new+GregorianCalendar();
++++cal.set(Calendar.YEAR,+2021);
++++cal.set(Calendar.MONTH,+0);
++++cal.set(Calendar.DATE,+1);
++++System.out.println("Original:+"+%2B+cal.getTime());
++++cal.add(Calendar.DATE,+-1);
++++System.out.println("After+adding+DATE:+"+%2B+cal.getTime());|code-block|syntax|javascript|1498900|输出：|1498901|Original:+Fri+Jan+01+15:08:33+CET+2021
After+adding+DATE:+Thu+Dec+31+15:08:33+CET+2020|1498902|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|T|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|V|8|@]|9|@]|A|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

I faced the same challenge where I needed to go back by 1 day (should be able to roll back by one even if previous day falls into previous year or months).
I did following, basically subtracted by 24 hours for 1 day.
someDateInGregorianCalendar.add(Calendar.HOUR, -24);
Alternatively, I could also do
<pre><code>GregorianCalendar cal = new GregorianCalendar();
 cal.set(Calendar.YEAR, 2021);
 cal.set(Calendar.MONTH, 0);
 cal.set(Calendar.DATE, 1);
 System.out.println(&quot;Original: &quot; + cal.getTime());
 cal.add(Calendar.DATE, -1);
 System.out.println(&quot;After adding DATE: &quot; + cal.getTime());
</code></pre>
OUTPUT:
<pre><code>Original: Fri Jan 01 15:08:33 CET 2021
After adding DATE: Thu Dec 31 15:08:33 CET 2020
</code></pre>

Anyone know a simple way using Java calendar to subtract X days from a date?

I have not been able to find any function which allows me to directly subtract X days from a date in Java. Can someone point me to the right direction?

How to subtract X days from a date using Java calendar?

Java

有人知道用Java日历从日期中减去X天的简单方法吗？在Java中，我找不到任何可以直接从日期中减去X天的函数。谁能给我指个方向？

问如何使用Java日历从日期中减去X天？
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