Fetch trip possibilities for these parameters
        http://webservices.ns.nl/ns-api-treinplanner?<parameters>
        fromStation
        toStation
        dateTime: 2012-02-21T15:50
        departure: true for starting at timestamp, false for arriving at timestamp
        previousAdvices
        nextAdvices

def get_trips(self, timestamp, start, via, destination, departure=True, prev_advices=1, next_advices=1):
        """
        Fetch trip possibilities for these parameters
        http://webservices.ns.nl/ns-api-treinplanner?<parameters>
        fromStation
        toStation
        dateTime: 2012-02-21T15:50
        departure: true for starting at timestamp, false for arriving at timestamp
        previousAdvices
        nextAdvices
        """
        timezonestring = '+0100'
        if is_dst('Europe/Amsterdam'):
            timezonestring = '+0200'
        url = 'http://webservices.ns.nl/ns-api-treinplanner?'
        url = url + 'fromStation=' + start
        url = url + '&toStation=' + destination
        if via:
            url = url + '&via=' + via
        if len(timestamp) == 5:
            # Format of HH:MM - api needs yyyy-mm-ddThh:mm
            timestamp = time.strftime("%Y-%m-%d") + 'T' + timestamp
            #requested_time = datetime.strptime(timestamp, "%Y-%m-%dT%H:%M")
            # TODO: DST/normal time
            requested_time = load_datetime(timestamp + timezonestring, "%Y-%m-%dT%H:%M%z")
        else:
            #requested_time = datetime.strptime(timestamp, "%d-%m-%Y %H:%M")
            requested_time = load_datetime(timestamp + timezonestring, "%d-%m-%Y %H:%M%z")
            timestamp = datetime.strptime(timestamp, "%d-%m-%Y %H:%M").strftime("%Y-%m-%dT%H:%M")
        url = url + '&previousAdvices=' + str(prev_advices)
        url = url + '&nextAdvices=' + str(next_advices)
        url = url + '&dateTime=' + timestamp
        raw_trips = self._request('GET', url)
        return self.parse_trips(raw_trips, requested_time)