Java库，将两个Date对象相加/相减，以毫秒为单位

long timeBetweenInMillis = d2.getTime() - d1.getTime();

Date.getTime()

Date d1 = 
Date d2 =
long intervalInMillis = d1.getTime() - d2.getTime();

long millis = date1.getTime() - date2.getTime();

import javax.xml.datatype.DatatypeFactory;
import javax.xml.datatype.XMLGregorianCalendar;

public class Demo {

    public static void main(String[] args) throws Exception {
        DatatypeFactory df = DatatypeFactory.newInstance();
        XMLGregorianCalendar date2 = df.newXMLGregorianCalendar(\"2011-05-29T22:50:12.692\");
        XMLGregorianCalendar date1 = df.newXMLGregorianCalendar(\"2011-03-29T22:50:12.692\");

        System.out.println(date2.toGregorianCalendar().getTimeInMillis() - date1.toGregorianCalendar().getTimeInMillis());
    }

}

Date result = new Date(d2.getTime() - d1.getTime());

d2.getTime() - d1.getTime() 

new Date(milliseconds);

Date result = new Date(Math.abs(d2.getTime() - d1.getTime()));