item.timestamp = ZonedDateTime.ofInstant(Instant.ofEpochMilli(timestamp), Clock.systemDefaultZone().getZone());
        return item;
    }

    public Map<String, Object> getUpdatedSource(final Map<String, Object> existingSource) {
        final Map<String, Object> map = new HashMap<>();
        map.put(FieldNames.TEXT, text);

        for (int i = 0; i < readings.length; i++) {