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JAVA UTC时间的基准点问题
计算机用的是unix纪元，1970年1月1日 0时0分 UTC(协调世界时 即升级版的格林威治时间)
可以说是英国标准时间。
中国是UTC+8 八区，中国本地时间要在以上标准时间上面加8小时。
反映在java的timemilli毫秒时是，
long china_ts=System.currentTimeMillier()+1000*60*60*8;
但只在不支持Java SE时区的早期版本(比如Java Card，Java ME/MIDP1.0)才需要自己手工加。
现在的java系统本身有时区库，用Calendar/Date类，会自动调整时区。不需要再手动算。按以上加法会画蛇添足。
关于JAVA时间格式转换问题，涉及时区
//我实现一个时钟窗口程序给你了，好让你更容易理解，希望对你有帮助。 import java.awt.*; import java.awt.event.*; import java.util.*; //世界时钟 public class TimerTest { public static void main(String[] args) { new TimerTestFrame("世界时钟"); } } class TimerTestFrame extends Frame { /** * */ private static final long serialVersionUID = 1L; public TimerTestFrame(String s) { super(s); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { dispose(); System.exit(0); } }); setLayout(new GridLayout(2, 6)); ClockCanvas clk1 = new ClockCanvas("北京", "GMT+8"); // 创建时钟 ClockCanvas clk2 = new ClockCanvas("巴黎", "GMT+2"); ClockCanvas clk3 = new ClockCanvas("华盛顿", "GMT-4"); ClockCanvas clk4 = new ClockCanvas("洛衫矶", "GMT-7"); ClockCanvas clk5 = new ClockCanvas("伦敦", "GMT+1"); ClockCanvas clk6 = new ClockCanvas("芝加哥", "GMT-5"); add(clk1); add(clk2); add(clk3); add(clk4); add(clk5); add(clk6); setSize(500, 350); // 设置框架宽高 setVisible(true); } } class ClockCanvas extends Canvas implements Runnable { /** * */ private static final long serialVersionUID = 1L; private int seconds = 0; private String city; private GregorianCalendar calendar; Thread t; public ClockCanvas(String c, String tz) { city = c; //也可以通过TimeZone.setTimeZone(String n)函数改变时区，n为时区参数名。 calendar = new GregorianCalendar(TimeZone.getTimeZone(tz)); t = new Thread(this); t.start(); setSize(125, 125); // 设置画布大小 setBackground(Color.black); } // 重写父类的方法绘制时钟图形 public void paint(Graphics g) { Graphics2D g2d = (Graphics2D) g; BasicStroke bstroke = new BasicStroke(2.0f); g2d.setStroke(bstroke); g2d.setColor(Color.green); g2d.drawOval(0, 0, 100, 100); bstroke = new BasicStroke(5.0f); g2d.setStroke(bstroke); g2d.drawLine(50, 0, 50, 5); g2d.drawLine(0, 50, 5, 50); g2d.drawLine(50, 95, 50, 98); g2d.drawLine(95, 50, 98, 50); double hourAngle = 2 * Math.PI * (seconds - 3 * 60 * 60) / (12 * 60 * 60); double minuteAngle = 2 * Math.PI * (seconds - 15 * 60) / (60 * 60); double secondAngle = 2 * Math.PI * (seconds - 15) / (60); bstroke = new BasicStroke(5.0f); g2d.setStroke(bstroke); g2d.drawLine(50, 50, 50 + (int) (30 * Math.cos(hourAngle)), 50 + (int) (30 * Math.sin(hourAngle))); bstroke = new BasicStroke(3.0f); g2d.setStroke(bstroke); g2d.drawLine(50, 50, 50 + (int) (40 * Math.cos(minuteAngle)), 50 + (int) (40 * Math.sin(minuteAngle))); bstroke = new BasicStroke(1.0f); g2d.setStroke(bstroke); g2d.drawLine(50, 50, 50 + (int) (45 * Math.cos(secondAngle)), 50 + (int) (45 * Math.sin(secondAngle))); g2d.setColor(Color.red); g2d.drawString(city, 35, 115); } public void timeElapsed() { //new Date()获得当前时间 System.out.println(new Date()); calendar.setTime(new Date()); seconds = calendar.get(Calendar.HOUR) * 60 * 60 + calendar.get(Calendar.MINUTE) * 60 + calendar.get(Calendar.SECOND); } public void run() { try { while (true) { Thread.sleep(300); timeElapsed(); repaint(); } } catch (InterruptedException e) { } } }
java中关于时区转换的问题
我倒是有个笨想法 截取最后5位与+0800比较（都先转成DATE类型） 少多少就在HOURS上加多少 如果加完后的HOURS数大于24 则HOURS-24并且DATE加1
java时间转换，带时区的
我假设了你的已知时间类型为Calendar，如果不是你也可以自己改成Date类型，代码如下：
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.TimeZone;
public class Test {
public static void main(String[] args) {
//假如这个是你已知的时间类型
Calendar cal = Calendar.getInstance();
cal.getTimeInMillis();
//北京时区GMT+8
Calendar beijingcal = Calendar.getInstance();
beijingcal.clear();
beijingcal.setTimeZone(TimeZone.getTimeZone("GMT+8"));
beijingcal.setTimeInMillis(cal.getTimeInMillis());
DateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String beijingFormatStr = fmt.format(beijingcal.getTime());
System.out.println(beijingFormatStr);
}
}
