Omit datetime from JSON conversion that converts from strings (#19807)

* Remove date object conversion as valueEditors don't seem to need it

* Update fault summary reference

* Added justification comment.

---------

Co-authored-by: Andy Butland <abutland73@gmail.com>

src/Umbraco.Core/PropertyEditors/PlainDateTimePropertyEditor.cs

@@ -13,7 +13,7 @@ namespace Umbraco.Cms.Core.PropertyEditors;
 public class PlainDateTimePropertyEditor : DataEditor
 {
     /// <summary>
-    ///     Initializes a new instance of the <see cref="PlainIntegerPropertyEditor" /> class.
+    ///     Initializes a new instance of the <see cref="PlainDateTimePropertyEditor" /> class.
     /// </summary>
     public PlainDateTimePropertyEditor(IDataValueEditorFactory dataValueEditorFactory)
         : base(dataValueEditorFactory)

src/Umbraco.Infrastructure/Serialization/JsonObjectConverter.cs

@@ -101,8 +101,15 @@ public sealed class JsonObjectConverter : JsonConverter<object>
             JsonTokenType.Number when reader.TryGetInt32(out int i) => i,
             JsonTokenType.Number when reader.TryGetInt64(out long l) => l,
             JsonTokenType.Number => reader.GetDouble(),
-            JsonTokenType.String when reader.TryGetDateTimeOffset(out DateTimeOffset datetime) => datetime,
-            JsonTokenType.String when reader.TryGetDateTime(out DateTime datetime) => datetime,
+
+            // DateTime and DateTimeOffset are not handled here, as in doing so we would convert strings that look like dates into dates,
+            // which, if coming fron a content property based on a text string property editor, isn't what we want.
+            // The date picker property editors work with strings, so this is fine.
+            // Testing also suggests other dates like for content content schedules aren't affected.
+            // See:
+            // - https://github.com/umbraco/Umbraco-CMS/issues/19360
+            // - https://github.com/umbraco/Umbraco-CMS/pull/19807
+
             JsonTokenType.String => reader.GetString(),
             _ => JsonDocument.ParseValue(ref reader).RootElement.Clone()
         };