Time and time zone in Java

For the Division of time zones, see Wikipedia: http://zh.wikipedia.org/wiki/%E6%99%82%E5%8D%80

In Java, the time class has two key classes:

Java. util. Calendar;

Java. util. Date;

When I was using the PostgreSQL database today, a timestamp with time zone was provided for the time type. I did not pay attention to the result. The time for writing data to the database is displayed on the page, but it does not reach the expected value, the problem is that the time format of this type is described in UTC. To correctly display the date of the local feature, additional processing is required.

I wrote a few tests to illustrate the time and time zone in Java.

1. Obtain the local Default Time Zone

@Test    public void test1() {        System.out.println("TimeZone.getDefault():" + TimeZone.getDefault());    }

Default Time Zone content:

TimeZone.getDefault():sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=19,lastRule=null]

2. Supported Time Zone Information

@Test    public void test3() {        String[] ids = TimeZone.getAvailableIDs();        System.out.println("TimeZone AvailableIDs Numbers :" + ids.length);        for (String id : ids) {            System.out.println("TimeZone:Id-" + id);        }    }

Partial results:

TimeZone AvailableIDs Numbers :619TimeZone:Id-Etc/GMT+12TimeZone:Id-Etc/GMT+11TimeZone:Id-Pacific/MidwayTimeZone:Id-Pacific/NiueTimeZone:Id-Pacific/Pago_PagoTimeZone:Id-Pacific/SamoaTimeZone:Id-US/SamoaTimeZone:Id-America/AdakTimeZone:Id-America/AtkaTimeZone:Id-Etc/GMT+10TimeZone:Id-HSTTimeZone:Id-Pacific/HonoluluTimeZone:Id-Pacific/JohnstonTimeZone:Id-Pacific/RarotongaTimeZone:Id-Pacific/TahitiTimeZone:Id-SystemV/HST10TimeZone:Id-US/AleutianTimeZone:Id-US/Hawaii

3. Display GMT time and local time

@Test    public void test2() {        Date d = new Date();        System.out.println("Date.toGMTString():" + d.toGMTString());        System.out.println("Date.toLocaleString():" + d.toLocaleString());    }

Result:

Date.toGMTString():29 Sep 2013 10:25:37 GMTDate.toLocaleString():2013-9-29 18:25:37

4. The following is a comparison between the time method of the Date object and the Calendar Object method.

Public void test4 () {Date d = new Date (); System. out. println ("java. util. date: "); System. out. println ("Date. getYear (): "+ d. getYear (); System. out. println ("Date. getMonth (): "+ d. getMonth (); System. out. println ("Date. getDay (): "+ d. getDay (); System. out. println ("Date. getHours (): "+ d. getHours (); System. out. println ("Date. getMinutes (): "+ d. getMinutes (); System. out. println ("Date. getSeconds (): "+ d. getSeconds ();} public void test10 () {/*** after JDK1.1: discard the Date class and use the Calendar class */Calendar c = Calendar. getInstance (); System. out. println ("YEAR:" + (c. get (Calendar. YEAR); System. out. println ("MONTH:" + (c. get (Calendar. MONTH) + 1); System. out. println ("DAY_OF_MONTH:" + (c. get (Calendar. DAY_OF_MONTH); System. out. println ("HOUR_OF_DAY:" + (c. get (Calendar. HOUR_OF_DAY); System. out. println ("MINUTE:" + (c. get (Calendar. MINUTE); System. out. println ("SECOND:" + (c. get (Calendar. SECOND); System. out. println ("DAY_OF_WEEK:" + (c. get (Calendar. DAY_OF_WEEK); System. out. println ("DAY_OF_WEEK_IN_MONTH:" + (c. get (Calendar. DAY_OF_WEEK_IN_MONTH); System. out. println ("DAY_OF_YEAR:" + (c. get (Calendar. DAY_OF_YEAR )));}

Result:

Date class: Result java. util. date: Date. getYear (): 113Date. getMonth (): 8Date. getDay (): 0Date. getHours (): 18Date. getMinutes (): 25Date. getSeconds (): 37Calendar class: result YEAR: 2013 MONTH: 9DAY_OF_MONTH: 29HOUR_OF_DAY: 18 MINUTE: 25 SECOND: 37DAY_OF_WEEK: 1DAY_OF_WEEK_IN_MONTH: 5DAY_OF_YEAR: 272

Most methods of the Date class have been deprecated. We recommend that you use the Calendar class. The Calendar class provides more complete functions and powerful time processing methods and attributes.

4. About the number of years and milliseconds

The year obtained by the Date instance is the difference between the current year and 1900.

GetTime () of the Date instance returns the current time distance: 00:00:00 milliseconds.

Yuan00:00:00. 000, gregali calendar, January 1, January 1, 1970, and 00:00:00. 000 on January 1, January 1, 1900 are important references for date and time in Java development.

5. UTC time

@Test    public void test5() {        long times = Date.UTC(2, 2, 1, 1, 1, 59);        System.out.println("Date.UTC(2, 2, 1, 1, 1, 59):" + times);        times = Date.UTC(113, 2, 1, 1, 1, 59);        System.out.println("Date.UTC(113, 2, 1, 1, 1, 59):" + times);    }

Result:

Date.UTC(2, 2, 1, 1, 1, 59):-2140815481000Date.UTC(113, 2, 1, 1, 1, 59):1362099719000

The time reference point here is: 00:00:00. 000, January 1, January 1, 1970.

A Time Zone diagram is attached:

650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131228/143RR019-0.jpg "title =" time zone chart "alt =" 191120811.jpg"/>

This article is from the "wild horse red dust" blog and will not be reposted!