Converting timezone for date using java
The method can be shortened a bit. It'll probably have some effect on perfomance as well.

public static Timestamp convertTimeZone(final Timestamp fromDate, final TimeZone fromTZ, final TimeZone toTZ ){

  // primitive long should be enough for his task
  final long timeInDate = fromDate.getTime();
  final int fromOffset = fromTZ.getOffset(timeInDate);
  final int toOffset = toTZ.getOffset(timeInDate);

  return new Timestamp(timeInDate + (toOffset - fromOffset));
}