We allow minus values for reminders, because all day event reminders …

…on that day are set with "minus minutes" (eg. -300)

lib/src/models/reminder.dart

@@ -4,9 +4,8 @@ class Reminder {
   /// The time when the reminder should be triggered expressed in terms of minutes before the start of the event
   int? minutes;
 
-  Reminder({@required this.minutes})
-      : assert(minutes != null && minutes >= 0,
-            'Minutes must be greater than or equal than zero');
+  //2.4.24 We allow minus values for reminders, because all day event reminders on that day are set with "minus minutes" (eg. -300)
+  Reminder({@required this.minutes}) : assert(minutes != null, 'Minutes must not be null');
 
   Reminder.fromJson(Map<String, dynamic> json) {
     minutes = json['minutes'] as int;