fix: #1942 utc timestamp being parsed as local time (#1953)

Author: richardshiue

frontend/appflowy_flutter/lib/plugins/database_view/calendar/application/calendar_bloc.dart

@@ -173,6 +173,7 @@ class CalendarBloc extends Bloc<CalendarEvent, CalendarState> {
 
       final date = DateTime.fromMillisecondsSinceEpoch(
         eventPB.timestamp.toInt() * 1000,
+        isUtc: true,
       );
       return CalendarEventData(
         title: eventPB.title,

frontend/appflowy_flutter/lib/plugins/database_view/widgets/row/cells/date_cell/date_cal_bloc.dart

@@ -264,7 +264,10 @@ Option<DateCellData> calDataFromCellData(DateCellDataPB? cellData) {
   Option<DateCellData> dateData = none();
   if (cellData != null) {
     final timestamp = cellData.timestamp * 1000;
-    final date = DateTime.fromMillisecondsSinceEpoch(timestamp.toInt());
+    final date = DateTime.fromMillisecondsSinceEpoch(
+      timestamp.toInt(),
+      isUtc: true,
+    );
     dateData = Some(DateCellData(
       date: date,
       time: time,

frontend/appflowy_flutter/lib/plugins/trash/src/trash_cell.dart

@@ -61,10 +61,12 @@ class TrashCell extends StatelessWidget {
   }
 
   String dateFormatter($fixnum.Int64 inputTimestamps) {
-    var outputFormat = DateFormat('MM/dd/yyyy hh:mm a');
-    var date =
-        DateTime.fromMillisecondsSinceEpoch(inputTimestamps.toInt() * 1000);
-    var outputDate = outputFormat.format(date);
+    final outputFormat = DateFormat('MM/dd/yyyy hh:mm a');
+    final date = DateTime.fromMillisecondsSinceEpoch(
+      inputTimestamps.toInt() * 1000,
+      isUtc: true,
+    );
+    final outputDate = outputFormat.format(date);
     return outputDate;
   }
 }