September Month Number: September is the 9th Month
What is the month number for September? If you’re filling out forms, coding, or just curious, the answer is simple: September is the 9th month of the year. But we’ve built a handy reference tool below so you can check any month’s number instantly.
Whether you need September’s number (9), its season (fall in the Northern Hemisphere), or how many days it has (30), this page has you covered. Use the interactive selector to explore all months.
Select any month below to see its number, days, and season.
* Months are numbered 1–12, with January as month 1.
Why Knowing the Month Number Matters
Month numbers are essential in many contexts:
- Forms & documents: Many official forms use numeric dates (MM/DD/YYYY).
- Programming: In JavaScript and other languages, months are often zero-indexed (0 = January).
- Data analysis: Sorting by month number is easier than by name.
- Planning: “Month 9” is quickly understood as September.
Complete Month Number Reference Table
| Month | Number | Days | Season (Northern) |
|---|---|---|---|
| January | 1 | 31 | Winter |
| February | 2 | 28/29 | Winter |
| March | 3 | 31 | Spring |
| April | 4 | 30 | Spring |
| May | 5 | 31 | Spring |
| June | 6 | 30 | Summer |
| July | 7 | 31 | Summer |
| August | 8 | 31 | Summer |
| September | 9 | 30 | Fall |
| October | 10 | 31 | Fall |
| November | 11 | 30 | Fall |
| December | 12 | 31 | Winter |
September: The 9th Month
September’s name comes from the Latin word septem, meaning seven — it was originally the 7th month in the Roman calendar before January and February were added. Today, it’s firmly the 9th month, with 30 days, and marks the beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere.
Quick Facts About September
- Number: 9
- Days: 30
- Birthstone: Sapphire
- Birth flowers: Aster and Morning Glory
- Zodiac signs: Virgo (until Sep 22) and Libra (Sep 23 onward)
Frequently Asked Questions About September’s Month Number
What is the month number for September?
September is the 9th month of the year. In numeric form, it’s represented as 09 or simply 9.
Is September the 9th or 10th month?
September is the 9th month. October is the 10th, November the 11th, and December the 12th.
Why is September called the 9th month when “sept” means seven?
In the ancient Roman calendar, March was the first month, so September was indeed the 7th month. When January and February were added later, September became the 9th month, but the name stuck.
How many days does September have?
September has 30 days. It’s one of four months with 30 days (April, June, September, November).
What season is September in?
In the Northern Hemisphere, September is in autumn/fall. In the Southern Hemisphere, it’s in spring.
What is September’s number in JavaScript?
In JavaScript, months are zero-indexed, so September is represented as 8 (January = 0, February = 1, … September = 8). But for human-friendly dates, it’s month 9.
What are the months in numbers 1-12?
1=January, 2=February, 3=March, 4=April, 5=May, 6=June, 7=July, 8=August, 9=September, 10=October, 11=November, 12=December.
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