getJulianDay method
获取儒略日 @return 儒略日
Implementation
double getJulianDay() {
int y = _year;
int m = _month;
double d = _day + ((_second * 1.0 / 60 + _minute) / 60 + _hour) / 24;
int n = 0;
bool g = false;
if (y * 372 + m * 31 + d.floor() >= 588829) {
g = true;
}
if (m <= 2) {
m += 12;
y--;
}
if (g) {
n = (y * 1.0 / 100).floor();
n = 2 - n + (n * 1.0 / 4).floor();
}
return ((365.25 * (y + 4716)).floor()) +
((30.6001 * (m + 1)).floor()) +
d +
n -
1524.5;
}