public static boolean isTimeZone(String format) {
if (format.equals("00:00"))
return true;
if (format.length() != 6)
return false;
if (!format.startsWith("+") && !format.startsWith("-"))
return false;
String subString = format.substring(1);
String arr[] = subString.split(":");
if (arr.length != 2)
return false;
if (arr[0].length() != 2 && arr[1].length() != 2)
return false;
try {
Integer.parseInt(arr[0]);
Integer.parseInt(arr[1]);