[solved] Various ways to calculate days between two dates

There are several ways to calculate the days between two dates.

public DateTest {

      //METHOD 1
      private int getDaysBetweetDates(Calendar day1, Calendar day2) {
            int days;
            Calendar dayOne = (Calendar) day1.clone(),
                   dayTwo = (Calendar) day2.clone();

           if (dayOne.get(Calendar.YEAR) == dayTwo.get(Calendar.YEAR)) {
               days = (dayTwo.get(Calendar.DAY_OF_YEAR) - dayOne.get(Calendar.DAY_OF_YEAR));
           } else if (dayTwo.get(Calendar.YEAR) > dayOne.get(Calendar.YEAR)) {
                  int extraDays = 0;

                  int dayTwoOriginalYearDays = dayTwo.get(Calendar.DAY_OF_YEAR);

                  while (dayTwo.get(Calendar.YEAR) > dayOne.get(Calendar.YEAR)) {
                         dayTwo.add(Calendar.YEAR, -1);
                        // getActualMaximum() important for leap years
                        extraDays += dayTwo.getActualMaximum(Calendar.DAY_OF_YEAR);
                  }
                  days = extraDays + dayTwoOriginalYearDays - dayOne.get(Calendar.DAY_OF_YEAR);
           } else {
                  days = 0;
           }
           return days;
      }

      //METHOD 2
      private int getDaysBetweenDates2(Calendar day1, Calendar day2){
             Calendar dayOne = (Calendar) day1.clone(),
                    dayTwo = (Calendar) day2.clone();
   
             long diff = dayTwo.getTimeInMillis() - dayOne.getTimeInMillis();
             return (diff /(24*60*60*1000));
      }

      //METHOD 3
       private float getDaysBetweenDates3(Calendar day1, Calendar day2){
           Calendar dayOne = (Calendar) day1.clone(),
                   dayTwo = (Calendar) day2.clone();
           long diff = dayTwo.getTimeInMillis() - dayOne.getTimeInMillis();
           return TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS);
      }

      public static void main(String[] args){
           DateTest test = new DateTest();

           long t1 = 1371773105000L;
           long t2 = 1372203030000L;

           Calendar d1 = Calendar.getInstance();
           d1.setTimeInMillis(t1);
        System.out.println("Date1: " + d1.get(Calendar.YEAR) + "/" + (d1.get(Calendar.MONTH)+1) + "/" + d1.get(Calendar.DAY_OF_MONTH));

           Calendar d2 = Calendar.getInstance();
           d2.setTimeInMillis(t2);
        System.out.println("Date2: " + d2.get(Calendar.YEAR) + "/" + (d2.get(Calendar.MONTH)+1) + "/" + d2.get(Calendar.DAY_OF_MONTH));

        System.out.println("Method1: "+ test.getDaysBetweenDates1(d1,d2));
        System.out.println("Method2: "+ test.getDaysBetweenDates2(d1, d2));
        System.out.println("Method3: "+ test.getDaysBetweenDates3(d1, d2));
}

The output:
Date1: 2013/6/20
Date2: 2013/6/25
Method1: 5
Method2: 4
Method3: 4


However, if you add the following lines to the beginning of Method 2 and Method 3. For example, the Method 2 will look like this.

      private int getDaysBetweenDates2(Calendar day1, Calendar day2){
            day1.set(Calendar.HOUR_OF_DAY, 1);
            day2.set(Calendar.HOUR_OF_DAY, 1);
            day1.set(Calendar.MINUTE, 1);
            day2.set(Calendar.MINUTE, 1);

             Calendar dayOne = (Calendar) day1.clone(),
                    dayTwo = (Calendar) day2.clone();
   
             long diff = dayTwo.getTimeInMillis() - dayOne.getTimeInMillis();
             return (diff /(24*60*60*1000));
      }

The output will become:
Date1: 2013/6/20
Date2: 2013/6/25
Method1: 5
Method2: 5
Method3: 5

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