We Keep Coding

Calendar.getInstance(TimeZone.getTimeZone("UTC")) is not returning UTC time

I am really confused with the result I am getting with Calendar.getInstance(TimeZone.getTimeZone("UTC")) method call, it's returning IST time.
Here is the code I used
Calendar cal_Two = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
System.out.println(cal_Two.getTime());
and the response I got is:
Sat Jan 25 15:44:18 IST 2014
So I tried changing the default TimeZone to UTC and then I checked, then it is working fine
Calendar cal_Two = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
System.out.println(cal_Two.getTime());
TimeZone tz = TimeZone.getDefault() ;
TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
Calendar cal_Three = Calendar.getInstance();
System.out.println(cal_Three.getTime());
TimeZone.setDefault(tz);
Result:
Sat Jan 25 16:09:11 IST 2014
Sat Jan 25 10:39:11 UTC 2014
Am I missing something here?

The System.out.println(cal_Two.getTime()) invocation returns a Date from getTime(). It is the Date which is getting converted to a string for println, and that conversion will use the default IST timezone in your case.
You'll need to explicitly use DateFormat.setTimeZone() to print the Date in the desired timezone.
EDIT: Courtesy of #Laurynas, consider this:
TimeZone timeZone = TimeZone.getTimeZone("UTC");
Calendar calendar = Calendar.getInstance(timeZone);
SimpleDateFormat simpleDateFormat =
new SimpleDateFormat("EE MMM dd HH:mm:ss zzz yyyy", Locale.US);
simpleDateFormat.setTimeZone(timeZone);
System.out.println("Time zone: " + timeZone.getID());
System.out.println("default time zone: " + TimeZone.getDefault().getID());
System.out.println();
System.out.println("UTC: " + simpleDateFormat.format(calendar.getTime()));
System.out.println("Default: " + calendar.getTime());

java.util.Date is independent of the timezone. When you print cal_Two though the Calendar instance has got its timezone set to UTC, cal_Two.getTime() would return a Date instance which does not have a timezone (and is always in the default timezone)
Calendar cal_Two = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
System.out.println(cal_Two.getTime());
System.out.println(cal_Two.getTimeZone());
Output:
Sat Jan 25 16:40:28 IST 2014
sun.util.calendar.ZoneInfo[id="UTC",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null]
From the javadoc of TimeZone.setDefault()
Sets the TimeZone that is returned by the getDefault method. If zone
is null, reset the default to the value it had originally when the VM
first started.
Hence, moving your setDefault() before cal_Two is instantiated you would get the correct result.
TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
Calendar cal_Two = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
System.out.println(cal_Two.getTime());
Calendar cal_Three = Calendar.getInstance();
System.out.println(cal_Three.getTime());
Output:
Sat Jan 25 11:15:29 UTC 2014
Sat Jan 25 11:15:29 UTC 2014

You are definitely missing a small thing and that is you are not setting a default value:
TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
So the code would look like:
TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
Calendar cal_Two = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
System.out.println(cal_Two.getTime());
Explanation: If you want to change the time zone, set the default time zone using TimeZone.setDefault()

Calendar currentTime = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
currentTime.set(Calendar.ZONE_OFFSET, TimeZone.getTimeZone("UTC").getRawOffset());
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, currentTime.get(Calendar.HOUR_OF_DAY));
calendar.getTimeInMillis()
is working for me

Following code is the simple example to change the timezone
public static void main(String[] args) {
//get time zone
TimeZone timeZone1 = TimeZone.getTimeZone("Asia/Colombo");
Calendar calendar = new GregorianCalendar();
//setting required timeZone
calendar.setTimeZone(timeZone1);
System.out.println("Time :" + calendar.get(Calendar.HOUR_OF_DAY)+":"+calendar.get(Calendar.MINUTE)+":"+calendar.get(Calendar.SECOND));
}
if you want see the list of timezones, here is the follwing code
public static void main(String[] args) {
String[] ids = TimeZone.getAvailableIDs();
for (String id : ids) {
System.out.println(displayTimeZone(TimeZone.getTimeZone(id)));
}
System.out.println("\nTotal TimeZone ID " + ids.length);
}
private static String displayTimeZone(TimeZone tz) {
long hours = TimeUnit.MILLISECONDS.toHours(tz.getRawOffset());
long minutes = TimeUnit.MILLISECONDS.toMinutes(tz.getRawOffset())
- TimeUnit.HOURS.toMinutes(hours);
// avoid -4:-30 issue
minutes = Math.abs(minutes);
String result = "";
if (hours > 0) {
result = String.format("(GMT+%d:%02d) %s", hours, minutes, tz.getID());
} else {
result = String.format("(GMT%d:%02d) %s", hours, minutes, tz.getID());
}
return result;
}

It is working for me.
Get in Timestamp type:
public static Timestamp getCurrentTimestamp() {
TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
final Calendar cal = Calendar.getInstance();
Date date = cal.getTime();
Timestamp ts = new Timestamp(date.getTime());
return ts;
}
Get in String type:
public static String getCurrentTimestamp() {
TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
final Calendar cal = Calendar.getInstance();
Date date = cal.getTime();
Timestamp ts = new Timestamp(date.getTime());
return ts.toString();
}

Try to use GMT instead of UTC. They refer to the same time zone, yet the name GMT is more common and might work.

Get correct long value from parsed Date (Timezone issue)

I'm trying to parse a date from a String and get the long value. The long value will be later sent to an SQL query.
here's my code:
String dayDate = "28-02-2013";
SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
Date day = new Date();
try {
day = sdf.parse(dayDate);
} catch (ParseException pe) {
pe.printStackTrace();
}
System.out.println("day : "+day.toString()+ " long : " + day.getTime());
which gives the following output:
day : Thu Feb 28 00:00:00 EET 2013 long : 1362002400000
which is correct but not what I want since the long value results in Wed, 27 Feb 2013 22:00:00 GMT (http://www.epochconverter.com/) (I'm in a GMT+2 timezone). And i need to send to correct long value to sql.
Is there anyway to work around this without using external libraries?

SimpleDateFormat is locale-aware, meaning the date it parses is in your timezone. Midnight 28 Feb in GMT+2 is actually 10pm 27 Feb in GMT, the long value 1362002400000. I would add this to get the parsing right (would't bother using Calendar):
sdf.setTimeZone(TimeZone.getTimeZone("GMT"))
Again, when you print this date it uses SimpleDateFormat and that's why you can see EET in the output.
Passing this to database is a different story though once you get this right.

Use DateFormat.setCalendar(Calendar cal) to set a Calendar with GMT as its timezone, or use DateFormat.setTimeZone(TimeZone zone) with the GMT TimeZone. That will ensure that the resulting Date will be 00:00:00 in GMT instead of in EET.

If you add a timezone specifier to your string you can force java to use GMT for the conversion:
String dayDate = "28-02-2013";
SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy z"); // z is a timezone specifier
Date day = new Date();
try {
day = sdf.parse(dayDate + " GMT"); // Use GMT timezone.
} catch (ParseException pe) {
pe.printStackTrace();
}
System.out.println("day : "+day.toString()+ " long : " + day.getTime());

You are converting between text and internal (Date) representations of dates and times without explicitly stating the time-zone. That never goes well.

Calendar calendar = Calendar.getInstance();
calendar.setTimeZone(TimeZone.getTimeZone("America/Los_Angeles"));
Date date = calendar.getTime();
Use your timezone String:
TimeZones

Local date & time to UTC and then UTC to local date & time

I am trying to convert locale time to UTC, and then UTC to locale time. But I am not getting the result.
public class DateDemo
{
public static void main(String args[])
{
DateFormat dateFormatter =
DateFormat.getDateTimeInstance
(DateFormat.SHORT, DateFormat.SHORT, Locale.getDefault());
TimeZone.setDefault(TimeZone.getDefault());
SimpleDateFormat simpleDateFormatter = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat simpleTimeFormatter = new SimpleDateFormat("hh:mm:ss a");
Date today = new Date();
String localeFormattedInTime = dateFormatter.format(today);
try
{
Date parsedDate = dateFormatter.parse(localeFormattedInTime);
System.out.println("Locale:" + localeFormattedInTime);
System.out.println("After parsing a date: " + parsedDate);
simpleDateFormatter.setTimeZone(TimeZone.getDefault());
simpleTimeFormatter.setTimeZone(TimeZone.getDefault());
String date = simpleDateFormatter.format(today);
String time = simpleTimeFormatter.format(today);
System.out.println("Today's only date: " + date);
System.out.println("Today's only time: " + time);
//// Locale to UTC converting
simpleDateFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
simpleTimeFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
String utcDate = simpleDateFormatter.format(today);
String utcTime = simpleTimeFormatter.format(today);
System.out.println("Convert into UTC's date: " + utcDate);
System.out.println("Convert into UTC's only time: " + utcTime);
//// UTC to locale converting
simpleDateFormatter.setTimeZone(TimeZone.getDefault());
simpleTimeFormatter.setTimeZone(TimeZone.getDefault());
Date getDate = simpleDateFormatter.parse(utcDate);
Date getTime = simpleTimeFormatter.parse(utcTime);
String getLocalDate = simpleDateFormatter.format(getDate);
String getLocalTime = simpleTimeFormatter.format(getTime);
System.out.println("Get local date: " + getLocalDate);
System.out.println("Get local time: " + getLocalTime);
} catch (ParseException e) {
e.printStackTrace();
}
}
}
I am sending local date & time to the web service, and then when require I need to retrieve the UTC date & time and then convert into locale date & time (i.e. user's local settings).
Sample Output:
Locale:11/9/12 8:15 PM
After parsing a date: Fri Nov 09 20:15:00 SGT 2012
Today's only date: 09/11/2012
Today's only time: 08:15:30 PM
Convert into UTC's date: 09/11/2012
Convert into UTC's only time: 12:15:30 PM
Get local date: 09/11/2012
Get local time: 12:15:30 PM
After Saksak & ADTC answers:
For the code fragment, UTC date & time (what is actually coming as GMT-5 because database may be in USA) is the input, and I want to get local date & time as output. But this following segment is still giving GMT-5 time.
SimpleDateFormat simpleDateTimeFormatter = new SimpleDateFormat("dd/MM/yyyy hh:mm:ss a");
....
Date inDateTime = simpleDateTimeFormatter.parse(intent.getExtras().getString("inTime")); Date outDateTime = simpleDateTimeFormatter.parse(intent.getExtras().getString("outTime"));
simpleDateTimeFormatter.setTimeZone(TimeZone.getDefault()); simpleDateTimeFormatter.setTimeZone(simpleDateTimeFormatter.getTimeZone());
//TimeZone tzTimeZone = TimeZone.getDefault();
//System.out.println("Current time zone: " + tzTimeZone.getDisplayName());
String getLocalInTimeString = simpleDateTimeFormatter.format(inDateTime);
String getLocalOutTimeString = simpleDateTimeFormatter.format(outDateTime);
My question: getLocalInTimeString & getLocalOutTimeString still showing GMT-5 timing. What's wrong here? Do I need to set any other things?

What you need to do to solve your problem is the following, you have your code to convert back to local time in this order :
simpleDateFormatter.setTimeZone(TimeZone.getDefault());
simpleTimeFormatter.setTimeZone(TimeZone.getDefault());
Date getDate = simpleDateFormatter.parse(utcDate);
Date getTime = simpleTimeFormatter.parse(utcTime);
and what you need to do is wait until you parse utcDate, utcTime Strings back to Date Object
then set the date formatter time zone to local zone as follows :
Date getDate = simpleDateFormatter.parse(utcDate);
Date getTime = simpleTimeFormatter.parse(utcTime);
simpleDateFormatter.setTimeZone(TimeZone.getDefault());
simpleTimeFormatter.setTimeZone(TimeZone.getDefault());
this should print the correct date/time in local.
Edit:
here is the full main method :
public static void main(String[] args) {
DateFormat dateFormatter = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, Locale.getDefault());
TimeZone.setDefault(TimeZone.getDefault());
SimpleDateFormat simpleDateFormatter = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat simpleTimeFormatter = new SimpleDateFormat("hh:mm:ss a");
Date today = new Date();
String localeFormattedInTime = dateFormatter.format(today);
try {
Date parsedDate = dateFormatter.parse(localeFormattedInTime);
System.out.println("Locale:" + localeFormattedInTime);
System.out.println("After parsing a date: " + parsedDate);
simpleDateFormatter.setTimeZone(TimeZone.getDefault());
simpleTimeFormatter.setTimeZone(TimeZone.getDefault());
String date = simpleDateFormatter.format(today);
String time = simpleTimeFormatter.format(today);
System.out.println("Today's only date: " + date);
System.out.println("Today's only time: " + time);
//// Locale to UTC converting
System.out.println("TimeZone.getDefault() >>> " + TimeZone.getDefault());
simpleDateFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
simpleTimeFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
String utcDate = simpleDateFormatter.format(today);
String utcTime = simpleTimeFormatter.format(today);
System.out.println("Convert into UTC's date: " + utcDate);
System.out.println("Convert into UTC's only time: " + utcTime);
//// UTC to locale converting
/**
** //////EDIT
*/
// at this point your utcDate,utcTime are strings that are formated in UTC
// so first you need to parse them back to Dates using UTC format not Locale
Date getDate = simpleDateFormatter.parse(utcDate);
Date getTime = simpleTimeFormatter.parse(utcTime);
// NOW after having the Dates you can change the formatters timezone to your
// local to format them into strings
simpleDateFormatter.setTimeZone(TimeZone.getDefault());
simpleTimeFormatter.setTimeZone(TimeZone.getDefault());
String getLocalDate = simpleDateFormatter.format(getDate);
String getLocalTime = simpleTimeFormatter.format(getTime);
System.out.println("Get local date: " + getLocalDate);
System.out.println("Get local time: " + getLocalTime);
} catch (ParseException e) {
e.printStackTrace();
}
}

Your problem is in lines 54 and 55:
Date getDate = simpleDateFormatter.parse(utcDate);
Date getTime = simpleTimeFormatter.parse(utcTime);
These lines are merely parsing Strings that contain the date and time, but these strings do not have any timezone information:
utcDate = "09/11/2012"
utcTime = "12:15:30 PM"
Therefore the parser assumes that the Strings are already in the locale of the timezone you set in lines 51 and 52.
Now think about how to fix it ;) HINT: Make sure the parser is assuming the correct timezone of the time represented by the strings.
PS: [RESOLVED!] I solved the problem but I discovered that the timezone conversion is erratic, for at least where I am. Time is 8:30 pm local. Convert to UTC, 12:30 pm (correct, 8 hr difference). Convert back, it's 8:00 pm (WRONG, eventhough the set timezone is correct - I got the original one and passed it back in - I'm only getting 7.5 hour difference). You should look for more reliable ways unless you can figure out what's going on and how to solve it.
[RESOLUTION:] The problem above was actually because the original code was splitting the date and time into two different parsers. If you use just one parser for both date and time combined you will get the correct date and time in the target locale. So in conclusion the parser is reliable but the way you use it makes a big difference!
SimpleDateFormat simpleDateTimeFormatter
= new SimpleDateFormat("dd/MM/yyyy hh:mm:ss a");
Date getDateTime
= simpleDateTimeFormatter.parse(utcDate + " " + utcTime);
//use above line if you have the date and time as separate strings
simpleDateTimeFormatter.setTimeZone(TimeZone.getDefault());
String getLocalDateTime = simpleDateTimeFormatter.format(getDateTime);
System.out.println("Get local date time: " + getLocalDateTime);
WHY USING TWO SEPARATE PARSERS FOR DATE AND TIME IS UNRELIABLE:
As explained above, it's a bad idea to use two separate parsers for date and time parts. Here's why:
Date getDate = simpleDateFormatter.parse(utcDate);
Date getTime = simpleTimeFormatter.parse(utcTime);
//Time zone changed to local here
String getLocalDate2 = simpleDateTimeFormatter.format(getDate);
String getLocalTime2 = simpleDateTimeFormatter.format(getTime);
System.out.println("Get local date2: " + getLocalDate2);
System.out.println("Get local time2: " + getLocalTime2);
OUTPUT:
Get local date2: 10/11/2012 08:00:00 AM
Get local time2: 01/01/1970 10:35:10 AM
I get the half hour difference because the default date 01/01/1970 is used in the Date variable storing time (second line). When this is converted to local timezone, the error happens as the formatter bases its conversion on the default date 01/01/1970 (where I live, the time difference was +7.5 hours in 1970 - today, it is +8 hours). This is why two separate parsers is not reliable even if you get the right result and you must always use a combined parser that accepts both date and time information.

Date/time conversion/arithmetic

I've below code in Java 1.7:
DateFormat df = DateFormat.getInstance();
Date startDate = df.parse("07/28/12 01:00 AM, PST");
The above date time (07/28/12 01:00 AM, PST) is in the properties file which is configurable. If this date time is already passed, then I need to get the current date, set the time part from above string which is 01:00 AM PST in the current date & if this time is also already passed, then get the next day & set the time part from above string in it. The final object should be Date since I need to use it in Timer object.
How can I do this efficiently? Should I convert from date to Calendar or vice-versa? Can any one provide snippet?

You should look into the Calendar class. You can use constructs like:
Calendar cal = Calendar.getInstance();
cal.setTime(startDate);
cal.add(Calendar.DAY_OF_YEAR, 1);
It also has methods for checking if your startDate is before() or after() a new date (use the current time).
While writing of the built-in Java date/time structure, i would be remiss if i didnt plug Joda Time, considered by many to be superior to the native Java implementation.
EDIT:
It would be more efficient to show an example of the Date.compareTo() process, as the Calendar.before() and Calendar.after() require comparisons against other Calendar objects, which can be expensive to create.
take a look at the following:
DateFormat df = DateFormat.getInstance();
Date startDate = df.parse("07/28/12 01:00 AM, PST");
Calendar cal = Calendar.getInstance();
cal.setTime(startDate);
Date now = new Date();
if (startDate.compareTo(now)< 0) {
System.out.println("start date: " + startDate + " is before " + now);
Calendar nowCal = Calendar.getInstance();
nowCal.add(Calendar.DAY_OF_YEAR,1);
cal.set(Calendar.DAY_OF_YEAR, nowCal.get(Calendar.DAY_OF_YEAR));
} else if (startDate.compareTo(now) == 0) {
System.out.println("startDate: " +startDate + " is equal to " + now);
} else {
System.out.println("startDate: " + cal + " is after " + now);
}
System.out.println(cal.getTime());

I think this should work...your algorthim has my head spinning a little and I'm in a different time zone, so you original string didn't work :P
try {
DateFormat df = DateFormat.getInstance();
Date startDate = df.parse("28/07/2012 01:00 AM");
System.out.println("StartDate = " + startDate);
Date callDate = startDate;
Calendar today = Calendar.getInstance();
Calendar start = Calendar.getInstance();
start.setTime(startDate);
System.out.println("Today = " + today.getTime());
// If this date time is already passed
// Tue Jul 31 12:18:09 EST 2012 is after Sat Jul 28 01:00:00 EST 2012
if (today.after(start)) {
//then I need to get the current date, set the time part from above string in the current date
Calendar timeMatch = Calendar.getInstance();
timeMatch.setTime(startDate);
timeMatch.set(Calendar.DATE, today.get(Calendar.DATE));
timeMatch.set(Calendar.MONTH, today.get(Calendar.MONTH));
timeMatch.set(Calendar.YEAR, today.get(Calendar.YEAR));
//& if this time is also already passed, then get the next day & set the time part from above string in it
if (timeMatch.after(today)) {
timeMatch.add(Calendar.DATE, 1);
}
callDate = timeMatch.getTime();
}
System.out.println("CallDate = " + callDate);
} catch (ParseException exp) {
exp.printStackTrace();
}
This produces the following output
StartDate = Sat Jul 28 01:00:00 EST 2012
Today = Tue Jul 31 12:18:09 EST 2012
CallDate = Tue Jul 31 01:00:00 EST 2012

Date and time conversion to some other Timezone in java

i have written this code to convert the current system date and time to some other timezone. I am not getting any error but i am not getting my output as expected. Like if i execute my program at a particular time.. My output is ::
The current time in India is :: Fri Feb 24 16:09:23 IST 2012
The date and time in :: Central Standard Time is :: Sat Feb 25 03:39:23 IST 2012
And the actual Time according to CST time zone is ::
Friday, 24 February 4:39:16 a.m(GMT - 6:00)
So there's some time gap. and i don't know why this is happening. Any help will be appreciated.. The code is ::
package MyPackage;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
public class Temp2 {
public static void main(String[] args) {
try {
Calendar currentdate = Calendar.getInstance();
String strdate = null;
DateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
strdate = formatter.format(currentdate.getTime());
TimeZone obj = TimeZone.getTimeZone("CST");
formatter.setTimeZone(obj);
//System.out.println(strdate);
//System.out.println(formatter.parse(strdate));
Date theResult = formatter.parse(strdate);
System.out.println("The current time in India is :: " +currentdate.getTime());
System.out.println("The date and time in :: "+ obj.getDisplayName() + "is ::" + theResult);
} catch (ParseException e) {
e.printStackTrace();
}
}
}

It's over the web. Could have googled. Anyways, here is a version for you (shamelessly picked and modified from here):
Calendar calendar = Calendar.getInstance();
TimeZone fromTimeZone = calendar.getTimeZone();
TimeZone toTimeZone = TimeZone.getTimeZone("CST");
calendar.setTimeZone(fromTimeZone);
calendar.add(Calendar.MILLISECOND, fromTimeZone.getRawOffset() * -1);
if (fromTimeZone.inDaylightTime(calendar.getTime())) {
calendar.add(Calendar.MILLISECOND, calendar.getTimeZone().getDSTSavings() * -1);
}
calendar.add(Calendar.MILLISECOND, toTimeZone.getRawOffset());
if (toTimeZone.inDaylightTime(calendar.getTime())) {
calendar.add(Calendar.MILLISECOND, toTimeZone.getDSTSavings());
}
System.out.println(calendar.getTime());

Your mistake is to call parse instead of format.
You call parse to parse a Date from a String, but in your case you've got a Date and need to format it using the correct Timezone.
Replace your code with
Calendar currentdate = Calendar.getInstance();
DateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
TimeZone obj = TimeZone.getTimeZone("CST");
formatter.setTimeZone(obj);
System.out.println("Local:: " +currentdate.getTime());
System.out.println("CST:: "+ formatter.format(currentdate.getTime()));
and I hope you'll get the output you are expecting.

SimpleDateFormat#setTimezone() is the answer. One formatter with ETC timezone you use for parsing, another with UTC for producing output string:
DateFormat dfNy = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.ROOT);
dfNy.setTimeZone(TimeZone.getTimeZone("EST"));
DateFormat dfUtc = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.ROOT);
dfUtc.setTimeZone(TimeZone.getTimeZone("UTC"));
try {
return dfUtc.format(dfNy.parse(input));
} catch (ParseException e) {
return null; // invalid input
}

Handling dates in Java in my daily work is a non-trivial task. I suggest you to use Joda-Time that simplify our coding days and you don't have to "re-invent the wheel".

You can use two SimpleDateFormat, one for parse the date string with EST timezone, one for print the date with UTC timezone
String format = "yyyy-MM-dd HH:mm:ss";
SimpleDateFormat estFormatter = new SimpleDateFormat(format);
estFormatter.setTimeZone(TimeZone.getTimeZone("EST"));
Date date = estFormatter.parse("2015-11-01 01:00:00");
SimpleDateFormat utcFormatter = new SimpleDateFormat(format);
utcFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println(utcFormatter.format(date));

You can just use "CST6CDT"
because in some countries they follow CDT in summer and CST in winter
public static String getDateInCST() {
Calendar calendar = Calendar.getInstance();
DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
formatter.setTimeZone(TimeZone.getTimeZone( "CST6CDT"));
String strdate = formatter.format(calendar.getTime());
TimeZone.getAvailableIDs();
return strdate;
}

Problem is when you print date obj it call toString method and it will print in your machines default time zone. Try this code and see difference.
Calendar currentdate = Calendar.getInstance();
String strdate = null;
DateFormat formatter = new SimpleDateFormat("dd-MM-yyyy HH:mm:ssz");
strdate = formatter.format(currentdate.getTime());
System.out.println("strdate=>" + strdate);
TimeZone obj = TimeZone.getTimeZone("CST");
formatter.setTimeZone(obj);
strdate = formatter.format(currentdate.getTime());
Date theResult = formatter.parse(strdate);
System.out.println("The current time in India is :: " +currentdate.getTime());
System.out.println("The date and time in :: " + obj.getDisplayName() + "is ::" + theResult);
System.out.println("The date and time in :: " + obj.getDisplayName() + "is ::" + strdate);

First message, don’t handle your date and time as strings in your code. Just as you don’t handle numbers and Boolean values as strings (I hope). Use proper date-time objects.
java.time
Sometimes we get date and time as string input. It may be from a text file, from the user or from data exchange with another system, for example. In those cases parse into a proper date-time object first thing. Second message, use java.time, the modern Java date and time API, for your date and time work.
DateTimeFormatter formatter
= DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss");
String input = "2015-11-01 01:00:00";
ZonedDateTime nyTime = LocalDateTime.parse(input, formatter)
.atZone(ZoneId.of("America/New_York"));
System.out.println("Time in New York: " + nyTime);
Output from this snippet is:
Time in New York: 2015-11-01T01:00-04:00[America/New_York]
To convert to GMT:
OffsetDateTime gmtTime = nyTime.toOffsetDateTime()
.withOffsetSameInstant(ZoneOffset.UTC);
System.out.println("GMT Time: " + gmtTime);
GMT Time: 2015-11-01T05:00Z
If you need to give string output, format using a date-time formatter. Here’s an example of formatting for an American audience:
DateTimeFormatter userFormatter
= DateTimeFormatter.ofLocalizedDateTime(FormatStyle.MEDIUM)
.withLocale(Locale.US);
String formattedDateTime = gmtTime.format(userFormatter);
System.out.println("GMT Time formatted for user: " + formattedDateTime);
GMT Time formatted for user: Nov 1, 2015, 5:00:00 AM
You additionally asked:
Between the two results below, which one should you take?
I understand that you ask because both are valid answers. On November 1, 2015 summer time (DST) ended at 2 AM. That is, after 01:59:59 came 01:00:00 a second time. So when we have got 2015-11-01 01:00:00 as input, it is ambiguous. It could be in Eastern Daylight Time, equal to 05:00 GMT, or it could be in Eastern Standard Time, one hour later, hence equal to 06:00 GMT. There is no way that I can tell you which of them is correct in your case. You may control which result you get using withEarlierOffsetAtOverlap() or withLaterOffsetAtOverlap(). Above we got the DST interpretation. So to get the standard time interpretation:
nyTime = nyTime.withLaterOffsetAtOverlap();
System.out.println("Alternate time in New York: " + nyTime);
Alternate time in New York: 2015-11-01T01:00-05:00[America/New_York]
We notice that the hour of day is still 01:00, but the offset is now -05:00 instead of -04:00. This also gives us a different GMT time:
GMT Time: 2015-11-01T06:00Z
GMT Time formatted for user: Nov 1, 2015, 6:00:00 AM
Avoid SimpleDateFormat and friends
While the other answers are generally correct, the classes DateFormat, SimpleDateFormat, Date and Calendar used there are poorly designed and long outdated. The first two are particularly troublesome. I recommend you avoid all of them. I frankly find the modern API so much nicer to work with.
Link
Oracle tutorial: Date Time explaining how to use java.time.

Please refer to below mentioned code.
DateFormat utcConverter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
utcConverter.setTimeZone(TimeZone.getTimeZone("GMT"));
String sampleDateTime = "2015-11-01 01:00:00";
DateFormat nyConverter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
nyConverter.setTimeZone(TimeZone.getTimeZone("EST"));
Calendar nyCal = Calendar.getInstance();
nyCal.setTime(nyConverter.parse(sampleDateTime));
System.out.println("NY TIME :" +nyConverter.format(nyCal.getTime()));
System.out.println("GMT TIME :" +utcConverter.format(nyCal.getTime()));

2020 Answer Here
If you want the new java.time.* feature but still want to mess with java.util.Date:
public static Date convertBetweenTwoTimeZone(Date date, String fromTimeZone, String toTimeZone) {
ZoneId fromTimeZoneId = ZoneId.of(fromTimeZone);
ZoneId toTimeZoneId = ZoneId.of(toTimeZone);
ZonedDateTime fromZonedDateTime =
ZonedDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault()).withZoneSameLocal(fromTimeZoneId);
ZonedDateTime toZonedDateTime = fromZonedDateTime
.withZoneSameInstant(toTimeZoneId)
.withZoneSameLocal(ZoneId.systemDefault())
;
return Date.from(toZonedDateTime.toInstant());
}
for java.sql.Timestamp
public static Timestamp convertBetweenTwoTimeZone(Timestamp timestamp, String fromTimeZone, String toTimeZone) {
ZoneId fromTimeZoneId = ZoneId.of(fromTimeZone);
ZoneId toTimeZoneId = ZoneId.of(toTimeZone);
LocalDateTime localDateTimeBeforeDST = timestamp.toLocalDateTime();
ZonedDateTime fromZonedDateTime = ZonedDateTime.of(localDateTimeBeforeDST, fromTimeZoneId);
ZonedDateTime toZonedDateTime = fromZonedDateTime.withZoneSameInstant(toTimeZoneId);
return Timestamp.valueOf(toZonedDateTime.toLocalDateTime());
}

For google calendar API
private String getFormatedDate(Date date)
{
DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss+05:30");
df.setTimeZone(TimeZone.getTimeZone("GMT+05:30"));
return df.format(date);
}