活用 gregoriancalendar 类的 gettimeinmillis() 方法。
注意，取到的值是从1970年1月1日00:00:00开始算起所经过的微秒数。一秒是一千微秒。

下面是自己写的一个例程及运行结果：

import java.util.gregoriancalendar;

class testclender {

public static void main (string args[]) {

gregoriancalendar ca = new gregoriancalendar();
system.out.println("ca: " + ca);
system.out.println("ca.time: " + ca.gettimeinmillis());

gregoriancalendar ca0 = new gregoriancalendar(2004-1900,11,31,23,59,59);
gregoriancalendar ca1 = new gregoriancalendar(2005-1900,00,01,00,00,02);
long sa = ca1.gettimeinmillis() - ca0.gettimeinmillis();
system.out.println("ca1-ca0: " + sa);

//2004.11.05 added
string old = "20041231235959";
int old_yyyy = integer.parseint(old.substring(0,4));
int old_mm = integer.parseint(old.substring(4,6));
int old_dd = integer.parseint(old.substring(6,8));
int old_hh = integer.parseint(old.substring(8,10));
int old_mi = integer.parseint(old.substring(10,12));
int old_ss = integer.parseint(old.substring(12,14));
string now = "20050101235959";
int now_yyyy = integer.parseint(now.substring(0,4));
int now_mm = integer.parseint(now.substring(4,6));
int now_dd = integer.parseint(now.substring(6,8));
int now_hh = integer.parseint(now.substring(8,10));
int now_mi = integer.parseint(now.substring(10,12));
int now_ss = integer.parseint(now.substring(12,14));
gregoriancalendar gcold = new gregoriancalendar(
old_yyyy-1900,old_mm-1,old_dd,old_hh,old_mi,old_ss);
gregoriancalendar gcnow = new gregoriancalendar(
now_yyyy-1900,now_mm-1,now_dd,now_hh,now_mi,now_ss);
sa = gcnow.gettimeinmillis() - gcold.gettimeinmillis();
system.out.println("now-old: " + sa);

}

}