fix: Correct DateTime to Timestamp conversions for timezone accuracy and ensure startTimestamp uses the full order.startDate.

apps/mobile/packages/data_connect/lib/src/services/data_connect_service.dart

@@ -171,16 +171,23 @@ class DataConnectService with DataErrorHandler, SessionHandlerMixin {
     }
   }
 
-  /// Converts a Data Connect [Timestamp] to a Dart [DateTime].
+  /// Converts a Data Connect [Timestamp] to a Dart [DateTime] in local time.
+  ///
+  /// Firebase Data Connect always stores and returns timestamps in UTC.
+  /// Calling [toLocal] ensures the result reflects the device's timezone so
+  /// that shift dates, start/end times, and formatted strings are correct for
+  /// the end user.
   DateTime? toDateTime(dynamic timestamp) {
     if (timestamp == null) return null;
     if (timestamp is fdc.Timestamp) {
-      return timestamp.toDateTime();
+      return timestamp.toDateTime().toLocal();
     }
     return null;
   }
 
   /// Converts a Dart [DateTime] to a Data Connect [Timestamp].
+  ///
+  /// Converts the [DateTime] to UTC before creating the [Timestamp].
   fdc.Timestamp toTimestamp(DateTime dateTime) {
     final DateTime utc = dateTime.toUtc();
     final int millis = utc.millisecondsSinceEpoch;