Fix bug on differential update

Author: julianrojas87

lib/Gtfsrt2LC.js

@@ -187,7 +187,7 @@ class Gtfsrt2LC {
                               ncu: await this.getStop(completedUpdates[j + 1].stopId),
                               pdIndex,
                               startTime: format(tripStartTime, 'H:mm:ss'),
-                              startDate,
+                              startDate: format(serviceDay, 'YYYYMMDD'),
                               departureDelay,
                               arrivalDelay,
                               type