Add support for parsing DateTime values

src/Core/Services/ExecutionHelper.cs

@@ -395,9 +395,74 @@ private static bool TryGetPropertyFromParent(
                 SupportedHotChocolateTypes.SINGLE_TYPE => value is IntValueNode intValueNode ? intValueNode.ToSingle() : ((FloatValueNode)value).ToSingle(),
                 SupportedHotChocolateTypes.FLOAT_TYPE => value is IntValueNode intValueNode ? intValueNode.ToDouble() : ((FloatValueNode)value).ToDouble(),
                 SupportedHotChocolateTypes.DECIMAL_TYPE => value is IntValueNode intValueNode ? intValueNode.ToDecimal() : ((FloatValueNode)value).ToDecimal(),
+                SupportedHotChocolateTypes.DATETIME_TYPE => ParseDateTimeValue(value.Value),
+                SupportedHotChocolateTypes.DATETIMEOFFSET_TYPE => ParseDateTimeOffsetValue(value.Value),
                 SupportedHotChocolateTypes.UUID_TYPE => Guid.TryParse(value.Value!.ToString(), out Guid guidValue) ? guidValue : value.Value,
                 _ => value.Value
             };
+
+            static object? ParseDateTimeValue(object? raw)
+            {
+                if (raw is null)
+                {
+                    return null;
+                }
+
+                if (raw is DateTime dt)
+                {
+                    return dt;
+                }
+
+                if (raw is DateTimeOffset dto)
+                {
+                    return dto.UtcDateTime;
+                }
+
+                if (raw is string s)
+                {
+                    // HotChocolate DateTime inputs are supplied as strings; parse them so DB providers
+                    // (notably PostgreSQL) receive a typed parameter instead of text.
+                    if (DateTimeOffset.TryParse(s, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out DateTimeOffset parsedDto))
+                    {
+                        return parsedDto.UtcDateTime;
+                    }
+
+                    if (DateTime.TryParse(s, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out DateTime parsedDt))
+                    {
+                        return parsedDt;
+                    }
+                }
+
+                return raw;
+            }
+
+            static object? ParseDateTimeOffsetValue(object? raw)
+            {
+                if (raw is null)
+                {
+                    return null;
+                }
+
+                if (raw is DateTimeOffset dto)
+                {
+                    return dto;
+                }
+
+                if (raw is DateTime dt)
+                {
+                    return new DateTimeOffset(dt);
+                }
+
+                if (raw is string s)
+                {
+                    if (DateTimeOffset.TryParse(s, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out DateTimeOffset parsedDto))
+                    {
+                        return parsedDto;
+                    }
+                }
+
+                return raw;
+            }
         }
 
         /// <summary>