Days until September 21
September 21 falls on a Monday in 2026 and a Tuesday in 2027. The count runs from today’s date on your device to the next September 21; pick another date to count from it instead.
- Days until September 21
- 356
From September 30, 2026, there are 356 days until September 21 on Tuesday, September 21, 2027.
- Date
- Tuesday, September 21, 2027
- Day of the week
- Tuesday
- In weeks
- 50 weeks and 6 days
Answer for the example date Wednesday, September 30, 2026. It changes to today's date when the page loads.
Days until September 21: 356. From September 30, 2026, there are 356 days until September 21 on Tuesday, September 21, 2027.
Where is September 21 on the calendar?
How to calculate
Counts the days from today, or any date you choose, to the next September 21, with its day of the week.
Example with the default inputs (Count from September 30, 2026) on the example date Wednesday, September 30, 2026: From September 30, 2026, there are 356 days until September 21 on Tuesday, September 21, 2027.
Method: Find the first September 21 on or after the start date, then count the days from the start date to it.
- September 21 comes every year, so the count is never more than 365 days.
- The start date itself is not counted: from the day before September 21, the count is 1; on September 21 itself, it is 0.
- Start dates from January 1, 1900 to December 31, 2400 work for the count to September 21, the range the date field accepts.
- Today is the date on your own device, so the count to September 21 changes at midnight where you are. Dates are whole calendar days, so a daylight-saving change never adds or loses a day.
Worked examples
Each example is checked against the calculator on every build.
- Count from 2027-09-21 gives Date 2027-09-21, Days until September 21 0.Source: U.S. Naval Observatory, Leap Years: the Gregorian leap year rule (https://aa.usno.navy.mil/faq/leap_years)
- Count from 2027-01-01 gives Date 2027-09-21, Days until September 21 263.Source: U.S. Naval Observatory, Leap Years: the Gregorian leap year rule (https://aa.usno.navy.mil/faq/leap_years)
- Count from 2027-09-22 gives Date 2028-09-21, Days until September 21 365.Source: U.S. Naval Observatory, Leap Years: the Gregorian leap year rule (https://aa.usno.navy.mil/faq/leap_years)
Other questions people ask
What day of the week is September 21?
Monday, September 21, 2026; Tuesday, September 21, 2027; Thursday, September 21, 2028. The weekday of September 21 moves on one day a year, or two when a February 29 falls between.
What day of the year is September 21?
September 21 is day 264 of a common year and day 265 of a leap year, such as 2028. Either way, 101 days of the year come after it.
What season is September 21 in?
In the Northern Hemisphere, September 21 is in summer in every year from 2026 to 2035; in the Southern Hemisphere, it is winter. Seasons here start on the astronomical equinoxes and solstices, dated in US Eastern Time.
Is September 21 a US federal holiday?
No. No US federal holiday falls on September 21. The next one in the calendar after September 21 is Columbus Day, which falls between October 8 and October 14.
How are the days until September 21 counted?
From the start date to September 21, without counting the start date: from September 20 the count is 1, and on September 21 it is 0. The day after, it moves on to the next September 21: from September 22, 2026, that is September 21, 2027, 364 days away.