I tried to set them equal to a variable to print on the main screen.
This is how you extract them to variables.
String localTimeStr = "local time : " + localTime;
String gmtStr = "time in GMT : " + converter.format(localTime);
System.out.println(localTimeStr);
System.out.println(gmtStr);
System.out.println() returns a void. You cannot assign that to anything.
[EDIT]
Since you're looking to print this on an Android screen use a Toast or find a text view and set it's text.