날짜 계산 하기 (시간 빼기)

int iYears = dtEnd.Year - dtBeg.Year;
int iMonths = dtEnd.Month - dtBeg.Month;
int iDays = dtEnd.Day - dtBeg.Day;

if (iDays < 0)
{
iDays += DateTime.DaysInMonth(dtEnd.Year, 1 + (dtEnd.Month + 10) % 12);
iMonths -= 1;
}
if (iMonths < 0)
{
iMonths += 12;
iYears -= 1;
}

Text = String.Format("{0} year{1}, {2} month{3}, {4} day{5}",
iYears, iYears == 1 ? "" : "s",
iMonths, iMonths == 1 ? "" : "s",
iDays, iDays == 1 ? "" : "s");