<UpdatedOn/>
<DeletedOn/>

[System.Xml.Serialization.XmlElementAttribute(DataType="date")]
[System.ComponentModel.DefaultValueAttribute(typeof(System.DateTime), "1901-01-01")]
public System.DateTime UpdateOn{...}

[Serializable]
public class Foo {
    [XmlIgnore]
    public DateTime Bar { get; set; }

    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    [XmlElement("Bar")]
    public string BarTransport {
        get {
            return Bar == DateTime.MinValue ? "" : XmlConvert.ToString(Bar);
        }
        set {
            Bar = string.IsNullOrEmpty(value) ? DateTime.MinValue
                : XmlConvert.ToDateTime(value);
        }
    }
}