[voraa]

class CDate extends Date {
	constructor (...args) {
		super (...args)
	}
	add (what) {
		if (what.seconds) {
			this.setTime(this.valueOf() + what.seconds*1000);
		}
		if (what.minutes) {
			this.setTime(this.valueOf() + what.minutes*60*1000);
		}
		if (what.hours) {
			this.setTime(this.valueOf() + what.hours*60*60*1000);
		}
		if (what.days) {
			this.setTime(this.valueOf() + what.days*24*60*60*1000);
		}
		if (what.weeks) {
			this.setTime(this.valueOf() + what.weeks*7*24*60*60*1000);
		}
		if (what.months) {
			let curm = this.getMonth();
			let cury = this.getFullYear();
			cury += what.months / 12 | 0;
			curm += what.months % 12; 
			if (curm >=12) {
				curm -= 12;
				cury ++;
			}
			const nd = new Date (cury, curm, 
				this.getDate(), this.getHours(), this.getMinutes(), this.getSeconds(), this.getMilliseconds());
			this.setTime(nd.valueOf());
		}
		if (what.years) {
			let cury = this.getFullYear() + what.years;
			const nd = new Date (cury, this.getMonth(), 
				this.getDate(), this.getHours(), this.getMinutes(), this.getSeconds(), this.getMilliseconds());
			this.setTime(nd.valueOf());
		}
	}
	sub (what) {
		this.add ({
			years: - (what.years||0),
			months: - (what.months||0),
			weeks: - (what.weeks||0),
			days: - (what.days||0),
			hours: - (what.hours||0),
			minutes: - (what.minutes||0),
			seconds: - (what.seconds||0),
		}
		)
	}
}


dt = new CDate();
console.log (dt)
dt.add({months:15, weeks:2, days:4, hours: 10, minutes:50})
console.log ('add', dt)

dt1 = new CDate();
console.log (dt1)
dt1.sub({years: 3, months:10, weeks:2, minutes:18})
console.log ('sub', dt1)