TimeZoneConvertor with DST

TimeZoneConvertor.java

import java.sql.Timestamp;
import java.util.TimeZone;
import java.util.logging.Logger;
import java.util.*;


public class TimeZoneConvertor {
	
	private static final TimeZone defaultTimeZone = TimeZone.getDefault();
	private static final Logger log = Logger.getLogger("TimeZone Convertor");
	
	/**
	 * Convert input time stamp to UTC/GMT
	 * @param timestamp
	 * @return
	 */
	public static Timestamp convertToUTC(Timestamp timestamp){
		return convert(timestamp,defaultTimeZone,null);
	}
	
	/**
	 * Convert from UTC/GMT
	 * @param timestamp
	 * @return
	 */
	public static Timestamp convertFromUTC(Timestamp timestamp){
		return convert(timestamp,null,defaultTimeZone);
	}
	
	/**
	 * Convert the Timestamp From one timezone to another
	 * 
	 * @param timestamp
	 * @param fromTimeZone
	 * @param toTimeZone
	 * @return
	 */
	private static Timestamp convert(Timestamp timestamp,TimeZone fromTimeZone, TimeZone toTimeZone) {
		
		long offFrom = fromTimeZone == null ? 0 : fromTimeZone.getOffset(timestamp.getTime());
		
		long offTo = toTimeZone == null ? 0 : toTimeZone.getOffset(timestamp.getTime());
		
		return new Timestamp(timestamp.getTime()/1000*1000 + timestamp.getNanos()/1000000 + offTo - offFrom);
	}
	
	public static void DisplayOffset(String text,int rawOffset,TimeZone timeZone){
		 int  hour = rawOffset/(60*60*1000);
		 int minutes = Math.abs(rawOffset/(60*1000)) % 60;
		 System.out.println(text+timeZone.getDisplayName()+ " "+hour+ ":"+minutes+" hours");
	}

	public static void main(String[] args) {
		
		Date date = new Date();
		Timestamp timestamp = new Timestamp(date.getTime());
		
		// To Get Available TimeZones
		/*String []TimezoneIDs = TimeZone.getAvailableIDs();
		for(String Id : TimezoneIDs)
		System.out.println("Timzone ID : \t"+Id);*/
		
		TimeZone fromTimeZone = TimeZone.getTimeZone("Asia/Kolkata");
		TimeZone toTimeZone = TimeZone.getTimeZone("America/Chicago");
		
		/*
		 * Now we have to convert from current timezone to target time 
		 * 
		 * First we have to convert the fromTimezone Time to GMT i.e difference with GMT
		 * 
		 * Get the converted timestamp i.e in GMT time now 
		 * 
		 * now convert timestamp from GMT to target time zone
		 */
		System.out.println("******************** Off set from GMT ************");
		DisplayOffset("From :   ", fromTimeZone.getRawOffset(), fromTimeZone);
		DisplayOffset("To :  ", toTimeZone.getRawOffset(), toTimeZone);
		System.out.println("Current Time    \t"+timestamp);
		timestamp = convert(timestamp, fromTimeZone, TimeZone.getTimeZone("GMT"));
		System.out.println("Timestamp to GMT\t"+timestamp);
		timestamp = convert(timestamp, TimeZone.getTimeZone("GMT"), toTimeZone);
		System.out.println("GMT to target Timezone \t"+timestamp);
		System.out.println("**************************************************");
	}

}