DateProblem.java

public static Calendar getBeginningOfMonth(Calendar date) {
    date.set(Calendar.DAY_OF_MONTH, 1);
    date.set(Calendar.HOUR_OF_DAY, 0);
    date.set(Calendar.MINUTE, 0);
    date.set(Calendar.SECOND, 0);
    date.set(Calendar.MILLISECOND, 0);
    return date;
}