TimeZone以及时区有关的操作Date/Calendar/SimpleDateFormat

TimeZone

1. System.getProperty("user.timezone")    System.setProperty("user.timezone","GMT+8")

2. TimeZone.getDefault().getID()                TimeZone.setDefault(TimeZone.getTimeZone("Asia/Shanghai"))

                Date date = new Date();System.out.println("date.toString():"+date.toString());System.out.println("date.getTime()"+date.getTime());Calendar cal = Calendar.getInstance();System.out.println("Calendar.getInstance().getTime():"+cal.getTime());System.out.println("Calendar.getInstance().getTimeInMillis():"+cal.getTimeInMillis());System.out.println("Calendar.getInstance().getTimeZone():"+cal.getTimeZone());System.out.println("system user.timezone:" + System.getProperty("user.timezone"));System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());System.out.println("--------------------------------------");System.out.println("After setTimeZone0:");TimeZone.setDefault(TimeZone.getTimeZone("GMT+2"));date = new Date();System.out.println("date.toString():"+date);System.out.println("date.getTime()"+date.getTime());cal = Calendar.getInstance();System.out.println("Calendar.getInstance().getTime():"+cal.getTime());System.out.println("Calendar.getInstance().getTimeInMillis():"+cal.getTimeInMillis());System.out.println("Calendar.getInstance().getTimeZone():"+cal.getTimeZone());System.out.println("system user.timezone:" + System.getProperty("user.timezone"));System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());System.out.println("--------------------------------------");TimeZone.setDefault(TimeZone.getTimeZone("Asia/Shanghai"));System.setProperty("user.timezone", "GMT+2");date = new Date();System.out.println("date.toString():"+date);System.out.println("date.getTime()"+date.getTime());cal = Calendar.getInstance();System.out.println("Calendar.getInstance().getTime():"+cal.getTime());System.out.println("Calendar.getInstance().getTimeInMillis():"+cal.getTimeInMillis());System.out.println("Calendar.getInstance().getTimeZone():"+cal.getTimeZone());System.out.println("system user.timezone:" + System.getProperty("user.timezone"));System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());System.out.println("--------------------------------------");

结果：

date.toString():Wed Nov 23 14:41:32 CST 2016date.getTime()1479883292507Calendar.getInstance().getTime():Wed Nov 23 14:41:32 CST 2016Calendar.getInstance().getTimeInMillis():1479883292535Calendar.getInstance().getTimeZone():sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=19,lastRule=null]system user.timezone:Asia/Shanghaisystem user.country:CN默认时区：Asia/Shanghai--------------------------------------After setTimeZone0:date.toString():Wed Nov 23 08:41:32 GMT+02:00 2016date.getTime()1479883292538Calendar.getInstance().getTime():Wed Nov 23 08:41:32 GMT+02:00 2016Calendar.getInstance().getTimeInMillis():1479883292538Calendar.getInstance().getTimeZone():sun.util.calendar.ZoneInfo[id="GMT+02:00",offset=7200000,dstSavings=0,useDaylight=false,transitions=0,lastRule=null]system user.timezone:Asia/Shanghaisystem user.country:CN默认时区：GMT+02:00--------------------------------------date.toString():Wed Nov 23 14:41:32 CST 2016date.getTime()1479883292539Calendar.getInstance().getTime():Wed Nov 23 14:41:32 CST 2016Calendar.getInstance().getTimeInMillis():1479883292539Calendar.getInstance().getTimeZone():sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=19,lastRule=null]system user.timezone:GMT+2system user.country:CN默认时区：Asia/Shanghai--------------------------------------

由此可见:

1）Date.toString()依赖于TimeZone中defaultTimezone；Calendar同样；TimeZone同样；

2）System.property 中 “user.timezone”与TimeZone中defaultTimezone的关系：

      TimeZone取默认值，先取该对象已经设定好的默认值，如果没有则取system.property中的"user.timezone",再没有的话才根据“java.home”和“user.country”来获取。。。。（从TimeZone.getDefault()源码可知)；

      System.property中user.timezone会在TimeZone执行由“java.home”和“user.country”获取timezone的方法后获得初值；

link:http://2005713.blog.51cto.com/1995713/698032

3）System.property中 “user.timezone"与 "user.country"无关；

4）Date.getTime() 和 Calendar.getTimeInMillis()相差无几，此毫秒数都是相对于1970.1.1 00:00:00  GMT.       

SimpleDateFormat

    

public class CalendarTest0 {   public static void main(String[] args) {String dateStr = null;SimpleDateFormat format = null;Date date = null;   System.out.println("system user.timezone:" + System.getProperty("user.timezone"));    System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");date = new Date();dateStr = format.format(date);System.out.println(dateStr);System.out.println("Set system.user.timezone=GMT+2:");System.setProperty("user.timezone", "GMT+2");   Calendar cal = Calendar.getInstance();format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");dateStr = format.format(cal.getTime());System.out.println(dateStr);System.out.println("system user.timezone:" + System.getProperty("user.timezone"));System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());System.out.println("------------------------------");System.out.println("Set system.user.timezone to GMT+2:");format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");date = new Date();    dateStr = format.format(date);    System.out.println(dateStr);System.out.println("system user.timezone:" + System.getProperty("user.timezone"));System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());    System.out.println("------------------------------");        System.out.println("Set format.settimezone to GMT+4:");    format  = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");    date = new Date();    format.setTimeZone(TimeZone.getTimeZone("GMT+4"));    dateStr = format.format(date);    System.out.println(dateStr);System.out.println("system user.timezone:" + System.getProperty("user.timezone"));System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());    System.out.println("------------------------------");    System.out.println("Set format.settimezone to GMT+6 and TimeZone.setTimeZone to GMT+8 :");    format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");    date = new Date();    format.setTimeZone(TimeZone.getTimeZone("GMT+6"));    TimeZone.setDefault(TimeZone.getTimeZone("GMT+8"));        dateStr = format.format(date);    System.out.println(dateStr);System.out.println("system user.timezone:" + System.getProperty("user.timezone"));System.out.println("system user.country:" + System.getProperty("user.country"));System.out.println("默认时区：" + TimeZone.getDefault().getID());    System.out.println("------------------------------");}}

Console:

system user.timezone:
system user.country:CN
默认时区：Asia/Shanghai
2016-11-24 18:34:43 +0800
Set system.user.timezone=GMT+2:
2016-11-24 18:34:43 +0800
system user.timezone:GMT+2
system user.country:CN
默认时区：Asia/Shanghai
------------------------------
Set system.user.timezone to GMT+2:
2016-11-24 18:34:43 +0800
system user.timezone:GMT+2
system user.country:CN
默认时区：Asia/Shanghai
------------------------------
Set format.settimezone to GMT+4:
2016-11-24 14:34:43 +0400
system user.timezone:GMT+2
system user.country:CN
默认时区：Asia/Shanghai
------------------------------
Set format.settimezone to GMT+6 and TimeZone.setTimeZone to GMT+8 :
2016-11-24 16:34:43 +0600
system user.timezone:GMT+2
system user.country:CN
默认时区：GMT+08:00
------------------------------

结论：

a.SimpleDateFormat使用的默认时区是TimeZone.getDefault()的时区而非System.getProperty("user.timezone")的时区；
b.SimpleDateFormat.setTimeZone()并不会改变TimeZone的值；
c.当既SimpleDateFormat.setTimeZone()又TimeZone.setDefault()时，SimpleDateFormat取SimpleDateFormat.setTimeZone()设定的值；