public void setFirstDate(int startYear, int startMonth) {
        this.startYear = startYear;
        this.startMonth = startMonth;
        selectedYear = startYear;
        selectedMonth = startMonth;
        selectedPosition = 0;
        if (adapter != null) {
            adapter.notifyDataSetChanged();
        }
    }
Color when month is before the current selected month
library/src/main/java/com/github/badoualy/datepicker/MonthView.java