September
September gets its name from Latin septem, meaning 'seven'. The oldest known Roman calendar had only ten months, starting from March, and September was originally the seventh month of the year. With the inclusion of January and February, September became the ninth month, but retained its original name.
Every year, September starts on the same day of the week as December. But another unique feature of this month is that it does not end on the same day of the week as any other month in the year. Take a calendar and check for yourself!