add proper converter for legacy datetime

Jellyfin.Api/TypeConverters/DateTimeTypeConverter.cs

@@ -0,0 +1,37 @@
+using System;
+using System.ComponentModel;
+using System.Globalization;
+
+namespace Jellyfin.Api.TypeConverters
+{
+    /// <summary>
+    /// Custom datetime parser.
+    /// </summary>
+    public class DateTimeTypeConverter : TypeConverter
+    {
+        /// <inheritdoc />
+        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        {
+            if (sourceType == typeof(string))
+            {
+                return true;
+            }
+
+            return base.CanConvertFrom(context, sourceType);
+        }
+
+        /// <inheritdoc />
+        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        {
+            if (value is string dateString)
+            {
+                if (DateTime.TryParseExact(dateString, "yyyyMMddHHmmss", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal, out var dateTime))
+                {
+                    return dateTime;
+                }
+            }
+
+            return base.ConvertFrom(context, culture, value);
+        }
+    }
+}

Jellyfin.Server/Startup.cs

@@ -1,4 +1,6 @@
-using System.Net.Http;
+using System;
+using System.ComponentModel;
+using Jellyfin.Api.TypeConverters;
 using Jellyfin.Server.Extensions;
 using Jellyfin.Server.Middleware;
 using Jellyfin.Server.Models;
@@ -94,6 +96,9 @@ namespace Jellyfin.Server
             });
 
             app.Use(serverApplicationHost.ExecuteHttpHandlerAsync);
+
+            // Add type descriptor for legacy datetime parsing.
+            TypeDescriptor.AddAttributes(typeof(DateTime?), new TypeConverterAttribute(typeof(DateTimeTypeConverter)));
         }
     }
 }