Usage Example::
        
            >>> timewrapper.day_interval(2014, 3, 1)
            (datetime(2014, 3, 1, 0, 0, 0), datetime(2014, 3, 1, 23, 59, 59))

def day_interval(year, month, day, return_str=False):
        """
        
        Usage Example::
        
            >>> timewrapper.day_interval(2014, 3, 1)
            (datetime(2014, 3, 1, 0, 0, 0), datetime(2014, 3, 1, 23, 59, 59))
        """
        start, end = datetime(year, month, day), datetime(year, month, day) + timedelta(days=1) - timedelta(seconds=1)
        if not return_str:
            return start, end
        else:
            return str(start), str(end)