There are four time zone in U.S.
PSF: Pacific Standard Time
MST: Mountain Standard Time
CST: Central Standard Time
EST: Eastern Standard Time
The function of transformation from UTC/GMT to local time
Sometimes you need to transform from standard time to local time.You can use the function bellow.
// Local Time -> UTC/GMT Time
public static long convertLocalTimeToUTC(long pv_localDateTime)
{
long lv_UTCTime = pv_localDateTime;
TimeZone z = TimeZone.getDefault();
//int offset = z.getRawOffset(); // The offset not includes daylight savings time
int offset = z.getOffset(pv_localDateTime); // The offset includes daylight savings time
lv_UTCTime = pv_localDateTime - offset;
return lv_UTCTime;
}
// UTC/GMT Time -> Local Time
public static long convertUTCToLocalTime(long pv_UTCDateTime)
{
long lv_localDateTime = pv_UTCDateTime;
TimeZone z = TimeZone.getDefault();
//int offset = z.getRawOffset(); // The offset not includes daylight savings time
int offset = z.getOffset(pv_UTCDateTime); // The offset includes daylight savings time
lv_localDateTime = pv_UTCDateTime + offset;
return lv_localDateTime;
}
It is very easy to understand.
You carefully check that the parameter with long type is return value from getDate() method in Date format.
Transform from UTC/GMT to local time using Date Format
Actually there is a need to change the form of the type such as "20120713064755".This is the solution using SimpleDateFormat.
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class ConverTimeZone {
public static void main(String[] args) {
// changes from UTC to local time
//String utcTime = "20120713184755";
String utcTime = "20120713064755";
String localTime = convertUtcToLocal(utcTime);
System.out.println("GMT/UTC: " + utcTime + ", local time: " + localTime);
}
/**
* the function that changes from UTC to local time
* @author xmlmanager
* @param utcTime GMT/UTC (format: 20120713064755)
* @return String local time
*/
private static String convertUtcToLocal(String utcTime) {
String localTime = "";
// declare date format
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
try {
// changes from UTC to Date format
Date dateUtcTime = dateFormat.parse(utcTime);
// changes from UTC Date format to the time of long type
long longUtcTime = dateUtcTime.getTime();
// calculate the difference through TimeZone (if it is summer time, use getOffset than getRawOffset)
TimeZone zone = TimeZone.getDefault();
int offset = zone.getOffset(longUtcTime);
long longLocalTime = longUtcTime + offset;
// changes from local time of long type to Date format
Date dateLocalTime = new Date();
dateLocalTime.setTime(longLocalTime);
// return the string of local time
localTime = dateFormat.format(dateLocalTime);
} catch (ParseException e) {
e.printStackTrace();
}
return localTime;
}
}
That's all!!
