Nullable Date Picker Property Value Converter for Umbraco

NullableDatePickerValueConverter.cs

public class NullableDatePickerValueConverter : DatePickerValueConverter
{
    public override Type GetPropertyValueType(IPublishedPropertyType propertyType) => typeof(DateTime?);

    public override object? ConvertSourceToIntermediate(
        IPublishedElement owner,
        IPublishedPropertyType propertyType,
        object source,
        bool preview)
    {
        if (source is string sourceString)
        {
            var attempt = sourceString.TryConvertTo<DateTime?>();
            return attempt.Success == false ? null : attempt.Result;
        }

        return source as DateTime?;
    }

    public override object? ConvertIntermediateToXPath(
        IPublishedElement owner,
        IPublishedPropertyType propertyType,
        PropertyCacheLevel referenceCacheLevel,
        object inter,
        bool preview)
    {
        var interDate = inter as DateTime?;

        if(interDate is null)
        {
            return null;
        }

        return XmlConvert.ToString(interDate.Value, XmlDateTimeSerializationMode.Unspecified);
    }
}