Calendar cal1 = getCalendarFromDate(mStartDate);
long startTime = cal1.getTimeInMillis();
Calendar cal2 = getCalendarFromDate(mEndDate);
long endTime = cal2.getTimeInMillis();
int numberOfDays = (int)(endTime - startTime)/(24 * 60 * 60 * 1000);
/**
* @param date format is 2012-9-18
* @return Calendar value is after set date's value
*/
private Calendar getCalendarFromDate(final String date) {
    int year = 0;
    int month = 0;
    int day = 0;
    try {
      String[] array = date.split("-");
      int[] arrayInt = new int[array.length];
      for (int i = 0; i < array.length; i++) {
        arrayInt[i] = Integer.parseInt(array[i]);
        if(i == 0) {
          year = arrayInt[0];
        } else if(i == 1){
          month = arrayInt[1];
        } else if(i == 2){
          day = arrayInt[2];
        }
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
    Calendar cal = Calendar.getInstance();
    if(year > 0 && month >= 0 && day >= 0) {
      cal.set(year, month, day);
    }
    return cal;
}