public Duration minus(long amount) {
        return new Minus().apply(this, unit == null ? FOREVER : new Duration(amount, unit));
    }
public Duration minus(long amount) {
        return new Minus().apply(this, unit == null ? FOREVER : new Duration(amount, unit));
    }
public Duration minus ( long amount ) { return new Minus ( ) . apply ( this , unit == null ? FOREVER : new Duration ( amount , unit ) ) ; }
Subtract an amount (with the same time unit as the current amount)

@param amount The amount to add
@return A new amount
Subtract an amount ( with the same time unit as the current amount )