Почему выдает разные значения при, казалось бы, одинаковых операциях с числами?

package com.javarush.task.task08.task0827;

import java.util.Date;

/*
Работа с датой
*/

public class Solution {
    public static void main(String[] args) {
        System.out.println(isDateOdd("JAN 1 2013"));
    }

    public static boolean isDateOdd(String date) {
        Date flyDate = new Date(date);
        flyDate.setHours(0);
        flyDate.setMinutes(0);
        flyDate.setSeconds(0);
        Date startYearDate = new Date();
        startYearDate.setYear(flyDate.getYear());
        startYearDate.setMonth(0);
        startYearDate.setDate(0);
        startYearDate.setHours(0);
        startYearDate.setMinutes(0);
        startYearDate.setSeconds(0);

        System.out.println(flyDate);
        System.out.println(startYearDate);
        System.out.println(flyDate.getTime());
        System.out.println(startYearDate.getTime());

        long timeInMsOfDay = 24*60*60*1000;
        long time1 = flyDate.getTime()/timeInMsOfDay;
        long time2 = startYearDate.getTime()/timeInMsOfDay;
        long differenseDays = (flyDate.getTime() - startYearDate.getTime())/timeInMsOfDay;

        System.out.println(time1-time2);
        System.out.println(differenseDays);




        return true;
    }
}