Java TimeZone Example

When you set a date-time value in java, you may encounter a timezone issue. You will find the date-time you get use java.util.Calendar class will always use the system default timezone. This example will tell you how to change it to show the date-time in your desired timezone.

1. java.util.TimeZone Properties And Methods.

  1. TimeZone.getDefault() : This method will return a java.util.TimeZone object which represent current system used timezone.
  2. TimeZone.getTimeZone(“Asia/Hong_Kong”) : This method will return a java.util.TimeZone object for a specified timezone id. You can click here to get all timezone id list.
  3. getDisplayName() : Return the time zone display name.
  4. getID() :  Return the timezone id. Such as “Pacific/Asia”.
  5. getOffset( long currentTimeMillis ) : Return offset milliseconds between UTC and the used timezone.

2. Show Specified TimeZone Info Example.

  1. The below java method will show the specified TimeZone info in the console.
    /* Show default or specified timezone info data. */
    public  void showSpecifiedTimeZoneInfo(String timeZoneId)
    {
        // Get current calendar.
        Calendar currCalendar = Calendar.getInstance();
    
        TimeZone targetTimeZone = null;
    
        if(timeZoneId==null || timeZoneId.trim().length()==0)
        {
            // Get default time zone.
            targetTimeZone = currCalendar.getTimeZone().getDefault();
        }else
        {
            // Get target time zone by id.
            targetTimeZone = TimeZone.getTimeZone(timeZoneId);
        }
    
        String targetTimeZoneDisplayName = targetTimeZone.getDisplayName();
        String targetTimeZoneId = targetTimeZone.getID();
        long targetTimeZoneOffSet = targetTimeZone.getOffset(System.currentTimeMillis());
        // Translate the milliseconds to hour.
        int offSetHour = (int)(targetTimeZoneOffSet / 1000 / 60 / 60);
    
        StringBuffer msgBuf = new StringBuffer();
        msgBuf.append("Time zone info. dislay name : ");
        msgBuf.append(targetTimeZoneDisplayName);
        msgBuf.append(" , id : ");
        msgBuf.append(targetTimeZoneId);
        msgBuf.append(" , offset hour : ");
        msgBuf.append(offSetHour);
    
        System.out.println(msgBuf.toString());
    }

3. Convert Date Time Between TimeZone Example.

  1. The below java methods will convert date-time between different TimeZones.
    // Show a given date time milliseconds value in different timezone.
    private void convertBetweenTimeZone(long milliseconds, String srcTimeZoneId, String destTimeZoneId)
    {
        if(srcTimeZoneId!=null && srcTimeZoneId.trim().length() > 0 && destTimeZoneId!=null && destTimeZoneId.trim().length() > 0) {
    
            // Get the source and destination timezone object.
            TimeZone srcTimeZone = TimeZone.getTimeZone(srcTimeZoneId);
    
            TimeZone destTimeZone = TimeZone.getTimeZone(destTimeZoneId);
    
            // Get calendar object.
            Calendar calendar = Calendar.getInstance();
            calendar.setTimeInMillis(milliseconds);
    
            calendar.setTimeZone(srcTimeZone);
            String srcDateTime = this.getDateTime(calendar);
    
            calendar.setTimeZone(destTimeZone);
            String destDateTime = this.getDateTime(calendar);
    
            System.out.println("Date milliseconds : " + milliseconds);
            System.out.println("Source date time : " + srcDateTime);
            System.out.println("Destination date time : " + destDateTime);
        }
    }
    
    // Show a given date time in different time zone.
    private void convertBetweenTimeZone(int year, int month, int day, int hour, int minute, int second, String srcTimeZoneId, String destTimeZoneId)
    {
        if(srcTimeZoneId!=null && srcTimeZoneId.trim().length() > 0 && destTimeZoneId!=null && destTimeZoneId.trim().length() > 0) {
            Calendar calendar = Calendar.getInstance();
            calendar.set(Calendar.YEAR, year);
            calendar.set(Calendar.MONTH, month - 1);
            calendar.set(Calendar.DAY_OF_MONTH, day);
            calendar.set(Calendar.HOUR_OF_DAY, hour);
            calendar.set(Calendar.MINUTE, minute);
            calendar.set(Calendar.SECOND, second);
    
            this.convertBetweenTimeZone(calendar.getTimeInMillis(), srcTimeZoneId, destTimeZoneId);
        }
    }
    
    /* Get special calendar date time in string format. */
    private String getDateTime(Calendar calendar)
    {
        StringBuffer strBuffer = new StringBuffer();
        strBuffer.append("Date time : ");
        strBuffer.append(calendar.get(Calendar.YEAR));
        strBuffer.append("-");
        strBuffer.append(calendar.get(Calendar.MONTH) + 1);
        strBuffer.append("-");
        strBuffer.append(calendar.get(Calendar.DAY_OF_MONTH));
        strBuffer.append(" ");
        strBuffer.append(calendar.get(Calendar.HOUR_OF_DAY));
        strBuffer.append(":");
        strBuffer.append(calendar.get(Calendar.MINUTE));
        strBuffer.append(":");
        strBuffer.append(calendar.get(Calendar.SECOND));
        strBuffer.append(" Zone Id : ");
        strBuffer.append(calendar.getTimeZone().getID());
    
        strBuffer.append(", Zone Offset : ");
    
        long zoneOffSet = calendar.get(Calendar.ZONE_OFFSET);
        // Translate the milliseconds to hour.
        int offSetHour = (int)(zoneOffSet / 1000 / 60 / 60);
        strBuffer.append(offSetHour);
        strBuffer.append(" hour");
        return strBuffer.toString();
    }
    
    public static void main(String args[])
    {
        TimeZoneExample timeZoneExample = new TimeZoneExample();
        timeZoneExample.showSpecifiedTimeZoneInfo("America/Jamaica");
    
        timeZoneExample.convertBetweenTimeZone(System.currentTimeMillis(), "America/Los_Angeles", "Asia/Singapore");
    
        timeZoneExample.convertBetweenTimeZone(2000, 1, 1, 10, 26, 26, "America/Los_Angeles", "Asia/Singapore");
    
    }
  2. Below is the example execution output.
    Date milliseconds : 1510222127526
    
    Source date time : Date time " 2021-11-9 2:8:47 Zone Id : America/Los_Angeles, Zone Offset : -8 hour
    
    Destination date time : Date time " 2021-11-9 18:8:47 Zone Id : Asia/Singapore, Zone Offset : 8 hour
    
    Date milliseconds : 946693586527
    
    Source date time : Date time " 2020-12-31 18:26:26 Zone Id : America/Los_Angeles, Zone Offset : -8 hour
    
    Destination date time : Date time " 2021-1-1 10:26:26 Zone Id : Asia/Singapore, Zone Offset : 8 hour
    
    
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