public Date(int year, int month, int day)
 {
     if (year >= 0)
     {
         Year = new Year(year);
     }
     if (month >= 0)
     {
         Month = new Month(month);
     }
     if (day >= 0)
     {
         Day = new Day(day);
     }
 }
 public ApproxDate(DateTimeOffset dt)
 {
     Year = new Year(dt.Year);
     Month = new Month(dt.Month);
     Day = new Day(dt.Day);
 }