The day of the week for September 9 varies by year. For example, in recent years:

• September 9, 2024, was a Monday.
• September 9, 2023, was a Saturday.
• September 9, 2022, was a Friday.
• September 9, 2021, was a Thursday.
• September 9, 2020, was a Wednesday

If you want to know the day of the week for September 9 of a specific year, please specify the year.