gistfile1.swift

import Foundation

extension Date {

    func add(years: Int = 0, months: Int = 0, days: Int = 0, hours: Int = 0, minutes: Int = 0, seconds: Int = 0) -> Date? {
        let comp = DateComponents(year: years, month: months, day: days, hour: hours, minute: minutes, second: seconds)
        return Calendar.current.date(byAdding: comp, to: self)
    }

    func subtract(years: Int = 0, months: Int = 0, days: Int = 0, hours: Int = 0, minutes: Int = 0, seconds: Int = 0) -> Date? {
        return add(years: -years, months: -months, days: -days, hours: -hours, minutes: -minutes, seconds: -seconds)
    }

}