Gregorian Gregorian::subtract_years(Gregorian const& date, year_t n) {
auto y = date.year() - n;
auto m = date.month();
auto d = date.day();
if (m == 2 && d == 29 && !is_gregorian_leapyear(y))
d = 28;
return Gregorian(year_t(y), month_t(m), day_t(d), date.hour(), date.minute(), date.second());
}
Gregorian Gregorian::add_months(Gregorian const& date, month_t n) {
/*auto m = date.month() + n;
auto y = date.year() + (m - 1) / 12;
m = (m - 1) % 12 + 1;
auto d = gregorian_days_in_month(m, is_gregorian_leapyear(y));
if (date.day() < d)
d = date.day();*/
year_t y = date.year() + n / 12;
month_t m = date.month() + n % 12;
auto adjust = (m - 1) / 12 + (m - 12) / 12;
y = y + adjust;
m = m - adjust * 12;
day_t d = min(date.day(), gregorian_days_in_month(m, is_gregorian_leapyear(y)));
return Gregorian(y, month_t(m), d, date.hour(), date.minute(), date.second());
}
Gregorian Gregorian::subtract_months(Gregorian const& date, month_t n) {
//auto m = date.month() - n;
//auto y = date.year() - (m - 1) / 12;
//m = (m - 1) % 12 + 1;
//auto d = gregorian_days_in_month(m, is_gregorian_leapyear(y));
//if (date.day() < d)
// d = date.day();
//return Gregorian(y, month_t(m), d, date.hour(), date.minute(), date.second());
year_t y = date.year() - n / 12;
month_t m = date.month() - n % 12;
auto adjust = (m - 1) / 12 + (m - 12) / 12;
y = y + adjust;
m = m - adjust * 12;
day_t d = min(date.day(), gregorian_days_in_month(m, is_gregorian_leapyear(y)));
return Gregorian(y, month_t(m), d, date.hour(), date.minute(), date.second());
}
inline hour_t hour(Gregorian const& greg) { return greg.hour(); }
