public static Calendar previous(Calendar self){
  Calendar result=(Calendar)self.clone();
  result.add(Calendar.DAY_OF_YEAR,-1);
  return result;
}

public static Calendar previous ( Calendar self ) { Calendar result = ( Calendar ) self . clone ( ) ; result . add ( Calendar . DAY_OF_YEAR , - 1 ) ; return result ; }
decrement a calendar by one day .
