What should be the best practice in Domain and DTO mapping

Question

I have task to make AbsenceDTO with two properties DateFrom and DateTO where the Domain Absence can be a single day with three properties Day, Month and Year. Bellow is the code sample:

public class Absence
{
    #region Properties

    /// <summary>
    /// A unique id
    /// </summary>
    public int Id { get; set; }

    /// <summary>
    /// Day of the absence
    /// </summary>
    public int Day { get; set; }

    /// <summary>
    /// Month of the absence
    /// </summary>
    public int Month { get; set; }

    /// <summary>
    /// Year of the absence
    /// </summary>
    public int Year { get; set; }

}

public class AbsenceDTO
{
    private List<Absence> absences = null;

    public AbsenceDTO()
    {

    }

    public AbsenceDTO(List<Absence> absences)
    {
        this.absences = absences;
    }


    public DateTime DateFrom
    {
        get 
        { 
           return //TO DO
        }
    }

    public DateTime DateTO
    {
        get 
        { 
           return //TO DO
        }
    }
}

So here how should I calculate DTO Date properties and what should be the best pattern/practice in making mapper/converter?