Introduction
Java 8 have a java.time package to work with the date and time API. The package includes many date and time classes.  For example: Calculate Number of Days between Two Dates.

private int getDays(String startDate, String presentDate) throws ParseException { SimpleDateFormat ddMMyyFormat = new SimpleDateFormat("yyyy-MM-dd"); String startDate = ddMMyyFormat.format(startDate); String promotionDate =ddMMyyFormat.format(presentDate); LocalDate sdate = LocalDate.parse(startDate); LocalDate pdate = LocalDate.parse(promotionDate); LocalDate ssdate = LocalDate.of(sdate.getYear(), sdate.getMonth(), sdate.getDayOfMonth()); LocalDate ppdate = LocalDate.of(pdate.getYear(), pdate.getMonth(), pdate.getDayOfMonth()); long dayLongObject=ChronoUnit.DAYS.between(ssdate, ppdate); int daysIntObject=(int)dayLongObject; System.out.println("Output is "+daysIntObject+" days"); return daysIntObject; }