How to get the timezone offset in GMT(Like GMT+7:00) from android device?

This might give you an idea on how to implement it to your liking:

Calendar mCalendar = new GregorianCalendar();  
TimeZone mTimeZone = mCalendar.getTimeZone();  
int mGMTOffset = mTimeZone.getRawOffset();  
System.out.printf("GMT offset is %s hours", TimeUnit.HOURS.convert(mGMTOffset, TimeUnit.MILLISECONDS)); 

(TimeUnit is "java.util.concurrent.TimeUnit")

This code return me GMT offset.

Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"),
                Locale.getDefault());
Date currentLocalTime = calendar.getTime();
DateFormat date = new SimpleDateFormat("Z");
String localTime = date.format(currentLocalTime);

It returns the time zone offset like this: +0530

If we use SimpleDateFormat below

DateFormat date = new SimpleDateFormat("z",Locale.getDefault());
String localTime = date.format(currentLocalTime);

It returns the time zone offset like this: GMT+05:30

Here is a solution to get timezone offset in GMT+05:30 this format

public String getCurrentTimezoneOffset() {

    TimeZone tz = TimeZone.getDefault();  
    Calendar cal = GregorianCalendar.getInstance(tz);
    int offsetInMillis = tz.getOffset(cal.getTimeInMillis());

    String offset = String.format("%02d:%02d", Math.abs(offsetInMillis / 3600000), Math.abs((offsetInMillis / 60000) % 60));
    offset = "GMT"+(offsetInMillis >= 0 ? "+" : "-") + offset;

    return offset;
}