public void set(int year, int month, int date) {
        this.year = year;
        this.month = month;
        this.date = date;

        pastDays = 0;

        pastDays += (year - 1) * 365 +
                        (year - 1) / 4 - (year - 1) / 100 + (year - 1) /400;

        for (int i = 0; i < month - 1; i++) {
            pastDays += monthDays[i];
            if (i == 1 && isLeapYear(year)) {
                pastDays++;
            }
        }

        pastDays += date;
    }