public class MyObj : BaseObj
{
    [XmlElement(Order = 0, ElementName = "name")]
    public string Name { get; set; }
    [XmlElement(Order = 1, ElementName = "xDate")]
    public DateTime? XDate { get; set; }
    [XmlElement(Order = 2, ElementName = "yDate")]
    public DateTime YDate { get; set; }

}

[Serializable]
public class BaseObj
{
    [XmlElement(Order = 0,ElementName = "pDate")]
    public DateTime? PDate { get; set; }
    [XmlElement(Order = 1, ElementName = "qDate")]
    public DateTime QDate { get; set; }
}

value.GetType().GetProperties().ToList().ForEach(
                m => { if (m.PropertyType.Equals(typeof(DateTime))) m.SetValue(value, DateTime.SpecifyKind((DateTime)m.GetValue(value), DateTimeKind.Utc)); });

public class MyObj : BaseObj
{
    [XmlElement(Order = 0, ElementName = "name")]
    public string Name { get; set; }
    [XmlElement(Order = 1, ElementName = "xDate")]
    public DateTime? XDate { get; set; }
    [XmlElement(Order = 2, ElementName = "yDate")]
    public DateTime YDate { get; set; }
    [XmlElement(Order = 3, ElementName = "kaBoom")]
    public AnotherObj KaBoom {get; set;} /*This contains a non-nullable DateTime member which causes the exception */
}

[Serializable]
public class AnotherObj
{
    [XmlElement(Order = 0,ElementName = "objID")]
    public int ObjID {get; set;}
    [XmlElement(Order = 1,ElementName = "anotherDate")]
    public DateTime AnotherDate {get; set;}
}