public class Order : Entity
    {
        public virtual DateTime OrderDate { get; set; }

        public virtual DateTime DeliveredDate { get; set; }
    }

class OrderMap : ClassMap<Order>
    {
        public OrderMap()
        {
            Id(x => x.ID).GeneratedBy.HiLo("100");

            Map(x => x.OrderDate).Not.Nullable().CustomSqlType("datetime2");

            Map(x => x.DeliveredDate).CustomSqlType("datetime2");
        }
    }

<property name="OrderDate" type="System.DateTime, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="OrderDate" not-null="true" sql-type="datetime2" />
</property>
    
<property name="DeliveredDate" type="System.DateTime, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="DeliveredDate" sql-type="datetime2" />
</property>

Map(x => x.OrderDate)
    .CustomType("DateTime2");

Map(x => x.DeliveredDate)
    .CustomType<DateTime2UserType>();