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Getting 4 hours difference while getting while converting data in to device timezone?

I am getting the 4 hours difference on time zone from below lines of code on my device:
I am getting the time in such a way like 2018-09-30T13:45:00Z
My start and End Date is as follow: -
"start_date":"2017-09-13T12:15:00Z",
"end_date":"2018-09-30T13:45:00Z",
Calendar c = Calendar.getInstance(Locale.getDefault());
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ss");
formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
Date localStartDate = formatter.parse(startTime);
Date localEndDate = formatter.parse(endTime);
SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm");
dateFormatter.setTimeZone(c.getTimeZone());
localStartDate = dateFormatter.parse(startTime);
localEndDate = dateFormatter.parse(endTime);
SimpleDateFormat monthFormat = new SimpleDateFormat("MMM");
monthFormat.setTimeZone(TimeZone.getTimeZone(TimeZone.getDefault().getDisplayName()));
String monthName = monthFormat.format(localStartDate);
eventDate.setMonth(monthName);
SimpleDateFormat dateFormat = new SimpleDateFormat("dd");
dateFormat.setTimeZone(TimeZone.getTimeZone(TimeZone.getDefault().getDisplayName()));
String dateName = dateFormat.format(localStartDate);
eventDate.setDate(dateName);
SimpleDateFormat dayNameFormat = new SimpleDateFormat("EEEE");
dayNameFormat.setTimeZone(TimeZone.getTimeZone(TimeZone.getDefault().getDisplayName()));
String dayName1 = dayNameFormat.format(localStartDate);
String dayName2 = dayNameFormat.format(localEndDate);
eventDate.setDayName1(dayName1);
eventDate.setDayName2(dayName2);
SimpleDateFormat timeFormat = new SimpleDateFormat("hh:mm a");
timeFormat.setTimeZone(TimeZone.getTimeZone(TimeZone.getDefault().getDisplayName()));
String startTimeName = timeFormat.format(localStartDate);
String endTimeName = timeFormat.format(localEndDate);
System.out.println("My Start date and end date==>>>"+startTimeName+" " +endTimeName );
Problem: Getting the 4 hours difference from above code, as I am setting my time zone to BOSTON(US), getting error.
My result from the below #Hugo solution is as below
And i am expecting the result as below
Please check it once..I have also set the TimeZone of Eastern DayLight Time but not getting proper solution..please check it once..And let me know

SimpleDateFormat and Calendar uses the JVM default timezone (unless you set a different one on them), and the default timezone can be different in each device/machine/environment. Not only that, this default can be changed without notice, even at runtime, so it's better to always make it explicit which one you're using.
When you do things like:
Calendar c = Calendar.getInstance(Locale.getDefault());
dateFormatter.setTimeZone(c.getTimeZone());
monthFormat.setTimeZone(TimeZone.getTimeZone(TimeZone.getDefault().getDisplayName()));
The Calendar is created with the default timezone, so dateFormatter will also have the same zone. So does monthFormat, and also the other formatters you created. The only formatter set to a different zone is the first one (which is set to UTC).
Also, the second formatter is redundant (it does the same thing that the first one is already doing: parsing the String to a Date), so you can remove it.
Assuming that your input is a String with the value 2018-09-30T13:45:00Z: the Z in the end indicates that this date is in UTC. So you should parse it using a formatter set to UTC. So, instead of using c.getTimeZone() and TimeZone.getDefault(), you should use only TimeZone.getTimeZone("UTC").
For the output, you must set the formatters with the timezone you want to convert to. If the timezone is "EDT", set to it (but don't use exactly "EDT", see below). If you want to use the JVM default, use TimeZone.getDefault() - just check this value before, to make sure the default is what you need.
Just keep in mind that short names like "EDT" and "EST" are not real timezones. Those abbreviations are ambiguous and not standard. Prefer to use IANA timezones names (always in the format Region/City, like America/New_York or Europe/Berlin).
So, when you do TimeZone.getTimeZone("EDT"), it usually returns "GMT" (because "EDT" is not recognized, and "GMT" is returned as default). That's because "EDT" is used by more than one timezone, so you must choose specifically which one you're using (I'm using America/New_York in these examples).
Another detail is that in the first 2 formatters you use hh, which means "hour of am/pm" (values from 1 to 12), but the input doesn't have AM/PM designators to properly resolve this. You need to change it to HH ("hour of day", with values from 0 to 23).
// input is in UTC
TimeZone inputZone = TimeZone.getTimeZone("UTC");
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
formatter.setTimeZone(inputZone);
Date localStartDate = formatter.parse(startTime);
Date localEndDate = formatter.parse(endTime);
...
// removed the second formatter (it was redundant)
// output is in EST (America/New_York)
// or use TimeZone.getDefault() to get JVM default timezone
TimeZone outputZone = TimeZone.getTimeZone("America/New_York");
SimpleDateFormat monthFormat = new SimpleDateFormat("MMM");
monthFormat.setTimeZone(outputZone);
...
SimpleDateFormat dateFormat = new SimpleDateFormat("dd");
dateFormat.setTimeZone(outputZone);
...
SimpleDateFormat dayNameFormat = new SimpleDateFormat("EEEE");
dayNameFormat.setTimeZone(outputZone);
...
SimpleDateFormat timeFormat = new SimpleDateFormat("hh:mm a");
timeFormat.setTimeZone(outputZone);
...
System.out.println("My Start date and end date==>>>" + startTimeName + " " + endTimeName);
With this, you're explicity using UTC for input and a specific timezone for output, instead of relying on the JVM default timezone (which can be different in each device and you can't control).
The output is:
My Start date and end date==>>>08:15 AM 09:45 AM
Java new Date/Time API
The old classes (Date, Calendar and SimpleDateFormat) have lots of problems and design issues, and they're being replaced by the new APIs.
In Android you can use the ThreeTen Backport, a great backport for Java 8's new date/time classes. To make it work, you'll also need the ThreeTenABP (more on how to use it here).
First you can use a org.threeten.bp.Instant to parse the input, because it's in UTC (designated by the Z in the end). Then you use a org.threeten.bp.ZoneId to convert it to a org.threeten.bp.ZonedDateTime:
// output timezone
// or use ZoneId.systemDefault() to get JVM default timezone
ZoneId zone = ZoneId.of("America/New_York");
// parse the inputs
ZonedDateTime startDate = Instant.parse(startTime).atZone(zone);
ZonedDateTime endDate = Instant.parse(endTime).atZone(zone);
Then you can use these objects to get the other fields:
// get month name
System.out.println(startDate.getMonth().getDisplayName(TextStyle.SHORT, Locale.getDefault()));
This is equivalent to MMM pattern, and it will print the month name in the default locale. If you want the month name in a specific language, just use another java.util.Locale value (such as Locale.ENGLISH or any other one as described in the javadoc).
The org.threeten.bp.format.TextStyle defines if the month name will be narrow (usually just one letter), short (usually 2 or 3 letters) or full (the full name). The output varies according to the locale used.
I personally prefer to not use the default locale, because it can be changed without notice, even at runtime. It's always better to specify the locale you want.
To get the day of month, you can choose to get it as an int or as a formatted String (using a org.threeten.bp.format.DateTimeFormatter):
// get day of month as int
int day = startDate.getDayOfMonth(); // 30
// get day of month as formatted string
String dayStr = DateTimeFormatter.ofPattern("dd").format(startDate); // 30
To get the day of week, it's similar to the code used to get the month:
// get day of week
System.out.println(startDate.getDayOfWeek().getDisplayName(TextStyle.FULL, Locale.getDefault()));
The same logic applies here: the TextStyle defines how the name will be (in this case, FULL is equivalen to EEEE, and it prints the full name), and the locale defines the language used.
Finally, to get the corresponding time, you can use another DateTimeFormatter:
// get time
DateTimeFormatter fmt = DateTimeFormatter.ofPattern("hh:mm a");
System.out.println(fmt.format(startDate)); // 08:15 AM
System.out.println(fmt.format(endDate)); // 09:45 AM
This will the date/time in the timezone you chose for the output.
If you're going to use the JVM default (ZoneId.systemDefault()), just check its value before to make sure it's the one you want (it might not be because this can be changed at runtime, so it's always better to specify one).

How to get android system date and time format in app

How can i get current time format that is set in android. Like it is 12 hrs or 24 hrs. I can easily get date and time and put format on it but i want to get current format of time from android system.

Use the following:
DateFormat.is24HourFormat(context);
Source: https://developer.android.com/reference/android/text/format/DateFormat.html#is24HourFormat(android.content.Context)

If you want to get a String you should use android.text.format.DateFormat
DateFormat dateFormat = android.text.format.DateFormat.getTimeFormat(context);
String = dateFormat.format(new Date());

How to change hours data from 24-hour format to 12-hour format?

I'm retrieving hours data for places from a service (Factual). It comes to me in 24-hour format and I need to display it in 12-hour format. The data for a specific day comes like this:
"sunday\":[[\"12:00\",\"21:30\"]]
I can successfully retrieve the hours from the JSON. Then, using SimpleDateFormat, I can parse the string to a Date object. But, then I can't figure out how to convert them to 12;-hour format so that I can display them as "12:00 - 9:30" or "12:00pm - 9:30pm" rather than "12:00 - 21:30".
How can I go about doing this? Thanks!
EDIT:
By parsing the string of hours (i.e. "12:00") using SimpleDateFormat sdf2 = new SimpleDateFormat("hh:mm a");, I get an error from JSON saying that the value is unparseable. If I use just SimpleDateFormat sdf2 = new SimpleDateFormat("hh:mm");, then there's no error but I can't get things to show up in 12-hour format.

If you look in the simple date format syntax docs you will find that 'h' is used for 12-hour time and 'a' is used for AM/PM. You will need to extract the two times using substring before putting them through the dateformatters.
http://developer.android.com/reference/java/text/SimpleDateFormat.html
SimpleDateFormat in = new SimpleDateFormat("<input format goes here>");
Date d = in.parse(INPUT_DATE_STRING);
SimpleDateFormat out = new SimpleDateFormat("<output format goes here>");
String outDate = out.format(d);

Try this:
//Char sequence for a 12 hour format.
CharSequence DEFAULT_FORMAT_12_HOUR = "hh:mm a";
//Char sequence for a 24 hour format.
CharSequence DEFAULT_FORMAT_24_HOUR = "kk:mm";
//date is the Date object. Look for more functions in format.
DateFormat.format(DEFAULT_FORMAT_12_HOUR, date);
Let me know if it works. If you have any issue check the Date you are sending.
//This should give you the default time on the device. To show that it works.
DateFormat.format(DEFAULT_FORMAT_12_HOUR, Calendar.getInstance());

Get days until date based on timezone on phone

I´ve been trying to figure this out for a while but can not wrap my head around it.
I´m working on an android app and i want to display left to a specific date, and i want the number of days based on what time zone i have set on my phone.
I have Joda Time in my app and the information i have is for example:
2013-05-05 9.00PM the time is in PST (GMT-8) timezone, i have no clue how to do this and i have searched both on google and SO but can not get a clear answer.
EDIT
I managed to solve my problem with code found here on SO
String dateString = airDate + " " + airTime.toUpperCase();
SimpleDateFormat sourceFormat = new SimpleDateFormat("yyyy-MM-dd K:mma");
sourceFormat.setTimeZone(TimeZone.getTimeZone("GMT-8"));
Date parsed;
parsed = sourceFormat.parse(dateString);
TimeZone tz = TimeZone.getDefault();
SimpleDateFormat destFormat = new SimpleDateFormat("yyyy-MM-dd");
destFormat.setTimeZone(tz);
result = destFormat.format(parsed);
However I found out that the times i first got isn´t correct and I now get the time zone in the format GMT-5 +DST. And I dont´t know what to do with the +DST if setting the time to 20:00 and using GMT-5 in my TimeZone.getTimeZone the time returned is 22:00 which is "wrong" since I live in sweden. I would appreciate any help with this.

If you could settle for a string that looks like "in 2 days", then you should be able to use DateUtils.getRelativeTimeSpanString().

Get time of different Time zones on selection of time from time picker

I have an issue of converting selected hours and minutes to different time zones of countries.
Supposing if i select 10 am in India then i want to know at 10 am in india what will be the time in USA/New york and Tokyo.and Vice versa.
Any help is appreciable...
Thank you

please find the sollution below :
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy hh:mma");
TimeZone timezone = TimeZone.getDefault();
TimeZone utcTimeZone = TimeZone.getTimeZone("UTC");
Date d = new Date();
sdf.setTimeZone(timezone);
String strtime = sdf.format(d);
Log.e("str time gmt ",strtime);
sdf.setTimeZone(utcTimeZone);
strtime = sdf.format(d);
Log.e("str time utc ",strtime);
i think this will solve your problem

You can probably use Joda Time - Java date and time API. You can get the DateTimeZone depending on the Canonical ID defined in the Joda Time,
DateTimeZone zone = DateTimeZone.forID("Asia/Kolkata");
Joda Time has a complete list of Canonical ID from where you can get TimeZone depending on the Canonical ID.
So, if you want to get the local time in New York at this very moment, you would do the following
// get current moment in default time zone
DateTime dt = new DateTime();
// translate to New York local time
DateTime dtNewYork = dt.withZone(DateTimeZone.forID("America/New_York"));
For getting more idea you can refer Changing TimeZone

Try using Joda-Time library
check the org.joda.time.DateTimeZone class
Here is the API documentation for the same.

you can also get it using , Here no external API is needed
DateFormat format = new SimpleDateFormat("MMMMM d, yyyy, h:mm a");
TimeZone utc = TimeZone.getTimeZone("America/New_York");
System.out.println(utc.getID());
GregorianCalendar gc = new GregorianCalendar(utc);
Date now = gc.getTime();
System.out.println(format.format(now));
you can see more time zone on this Link
Output
America/New_York
December 29, 2012, 11:04 AM
If you don't know city name then you can also use it by Zone name as follow
DateFormat format = new SimpleDateFormat("MMMMM d, yyyy, h:mm a");
TimeZone cst = TimeZone.getTimeZone("US/Eastern");
System.out.println(cst.getID());
GregorianCalendar gc = new GregorianCalendar(cst);
Date now = gc.getTime();
format.setTimeZone(cst);
System.out.println(format.format(now))
Output
US/Eastern
December 29, 2012, 12:38 AM

Not really sure about the solution I'm going to provide but I think you can try it. GMT (Greenwich Mean Time) is a standard. I think you can keep it as a base and calculate the desired time. GMT standard is easily available too.
For example: While installing an OS like Windows XP or Windows 7, we select the time from a drop down menu. My point is, keeping this as the base, you can find the difference between the time zones in NY-US and Tokyo-Japan or vice versa as you desire it.
Hope this helps.