fix: allow dates before unix epoch (#8681)

Author: kaluli123123

frontend/appflowy_flutter/lib/workspace/presentation/widgets/date_picker/widgets/date_picker.dart

@@ -4,7 +4,10 @@ import 'package:flutter/material.dart';
 import 'package:table_calendar/table_calendar.dart';
 import 'package:universal_platform/universal_platform.dart';
 
-final kFirstDay = DateTime.utc(1970);
+// Dates are also used for values such as birthdays, which can predate Unix
+// epoch. Keep the lower bound broad enough for historical dates while avoiding
+// the impractically large range before the Gregorian calendar.
+final kFirstDay = DateTime.utc(1900);
 final kLastDay = DateTime.utc(2100);
 
 class DatePicker extends StatefulWidget {

frontend/appflowy_flutter/test/widget_test/date_picker_test.dart

@@ -178,6 +178,29 @@ void main() {
       );
 
   group('AppFlowy date picker:', () {
+    testWidgets('supports dates before the Unix epoch', (tester) async {
+      await tester.pumpWidget(
+        const WidgetTestApp(
+          child: _MockDatePicker(),
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      final calendar = tester.widget<TableCalendar>(
+        find.byType(TableCalendar),
+      );
+      expect(calendar.firstDay, DateTime.utc(1900));
+
+      final dateTextField = find.byKey(
+        const ValueKey('date_time_text_field_date'),
+      );
+      await tester.enterText(dateTextField, 'Jan 25, 1958');
+      await tester.testTextInput.receiveAction(TextInputAction.done);
+      await tester.pumpAndSettle();
+
+      expect(getMockState(tester).data.dateTime, DateTime(1958, 1, 25));
+    });
+
     testWidgets('default state', (tester) async {
       await tester.pumpWidget(
         const WidgetTestApp(