Fourth week. The fourth week in a month differs from the other three weeks in the month in
compiling and reporting railroad earnings. The first seven days are counted as the first week, the
second seven days as the second week and the third seven days as the third week, while the
remaining days of the month are counted as the fourth week. In a month of 30 days the fourth
week consists of nine days and in a month of 31 days it consists of ten days. Thus, the fourth
week may contain two Sundays.  For additional information see Railroad earnings.