public void ChangeDate(ATimeSpan span, int direction)
{
//
// First, calculate new Hour,Minute,Second
//
double hms1 = this.Hour * 60.0 * 60.0 + this.Minute * 60.0 + this.Second;
double hms2 = span.Hour * 60.0 * 60.0 + span.Minute * 60.0 + span.Second;
hms1 += hms2 * direction;
int day;
if (0.0 <= hms1 && hms1 < 24.0 * 60.0 * 60.0)
{
day = 0;
}
else if (hms1 >= 24.0 * 60.0 * 60.0)
{
day = (int)Math.Floor(hms1 / 24.0 / 60.0 / 60.0);
hms1 = UdMath.fmod(hms1, 24.0 * 60.0 * 60.0);
}
else
{
day = (int)Math.Ceiling(hms1 / 24.0 / 60.0 / 60.0) - 1;
hms1 = UdMath.fmod(hms1, 24.0 * 60.0 * 60.0) + 24.0 * 60.0 * 60.0;
}
int newHour = (int)Math.Floor(hms1 / 60.0 / 60.0);
int newMin = (int)Math.Floor(hms1 / 60.0) - newHour * 60;
double newSec = hms1 - ((double)newHour * 60.0 * 60.0 + (double)newMin * 60.0);
//
// Next, calculate new Year, Month, Day
//
ATime newDate = new ATime(this.Year, this.Month, this.Day, 12, 0, 0.0, 0.0);
double jd = newDate.JD;
jd += day + span.Day * direction;
newDate = new ATime(jd, 0.0);
int newYear = newDate.Year;
int newMonth = newDate.Month;
int newDay = newDate.Day;
newMonth += span.Month * direction;
if (1 > newMonth)
{
newYear -= newMonth / 12 + 1;
newMonth = 12 + newMonth % 12;
}
else if (newMonth > 12)
{
newYear += newMonth / 12;
newMonth = 1 + (newMonth - 1) % 12;
}
newYear += span.Year * direction;
// check bound between julian and gregorian
if (newYear == 1582 && newMonth == 10)
{
if (5 <= newDay && newDay < 10)
{
newDay = 4;
}
else if (10 <= newDay && newDay < 15)
{
newDay = 15;
}
}
newDate = LimitATime(new ATime(newYear, newMonth, newDay, 12, 0, 0, 0.0));
newYear = newDate.Year;
newMonth = newDate.Month;
newDay = newDate.Day;
this.Year = newYear;
this.Month = newMonth;
this.Day = newDay;
this.Hour = newHour;
this.Minute = newMin;
this.Second = newSec;
this.JD = GetJD() - this.Timezone / 24.0;
this.T = GetT();
this.T2 = GetT2();
}