Write Event To gmail calendar

Hi

I aam attempting to write an event to gmail calendar based on the code from https://docs.microsoft.com/en-us/xamarin/android/user-interface/controls/calendar

        ContentValues eventValues1 = new ContentValues();

        eventValues1.Put(CalendarContract.Events.InterfaceConsts.CalendarId,
            s1);
        eventValues1.Put(CalendarContract.Events.InterfaceConsts.Title,
            "Test Event from M4A");
        eventValues1.Put(CalendarContract.Events.InterfaceConsts.Description,
            "This is an event created from Xamarin.Android");
        eventValues1.Put(CalendarContract.Events.InterfaceConsts.Dtstart,
            MyUtils.GetDateTimeMS(2020, 08, 25, 12, 15));
        eventValues.Put(CalendarContract.Events.InterfaceConsts.Dtend,
            MyUtils.GetDateTimeMS(2020, 08, 25, 13, 15));


        eventValues1.Put(CalendarContract.Events.InterfaceConsts.EventTimezone, tz.Id);
        eventValues1.Put(CalendarContract.Events.InterfaceConsts.EventEndTimezone, tz.Id);



        var uri2 = ContentResolver.Insert(CalendarContract.Events.ContentUri,
            eventValues1);

i get an error saying "DTEND and DURATION cant both be null for an event??

Suggestions?

Regards
M.R.