Days difference between dates

I am trying to find days difference between two dates. I am using JDK 1.7 (cannot change it). Somehow JDK ignores March 9th in difference calculations, while JODA API calculates it correctly. Here is the code i executed using TimeUnit and JODA API.

    String dateStart = "11/16/2019 00:00:00";
    String dateStop = "05/15/2020 00:00:00";
    SimpleDateFormat format2 = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");
    firstDate = format2.parse(dateStart);
    secondDate = format2.parse(dateStop);

    long diffInMillies =  secondDate.getTime() - firstDate.getTime();
    long diff = TimeUnit.DAYS.convert(diffInMillies, TimeUnit.MILLISECONDS);
    System.out.println(">>>>>>>>>>>>");
    System.out.println("difference in days is  " + diff);

   // Days.bet(firstDate, secondDate);
    DateTime dateTime1 = new DateTime(firstDate.getTime());
    DateTime dateTime2 = new DateTime(secondDate.getTime());
    System.out.println("Difference by JODA API " +  Days.daysBetween(dateTime1,dateTime2 ).getDays());

Here the output i got, Seems a bug in JDK. Could anyone please let me know if i am mistaken.

Difference in days is  180
Difference by JODA API 181