What is the Days Until Fall Calculator?
This tool counts how many days remain until the start of fall (autumn) in the Northern Hemisphere. Fall traditionally begins around the September equinox, which this calculator fixes at September 22. Enter any date and it tells you how long until autumn arrives. Note: in the Southern Hemisphere the seasons are reversed, so this date marks the start of spring there.
How to use it
Pick the date you want to count from (it defaults to today) and the calculator returns the number of days until the next September 22. If that date has already passed in the current year, it automatically rolls forward to next year's autumn.
The formula explained
The calculation is a simple date difference:
$$\text{days} = \text{date(September 22, next occurrence)} - \text{from date}$$
The "next occurrence" rule ensures the countdown is always positive: once September 22 of the current year is behind you, the target jumps to September 22 of the following year.
Worked example
Suppose today is September 1, 2024. September 22, 2024 is still ahead, so the target stays in 2024. From September 1 to September 22 there are 21 days. The calculator therefore returns 21 days, or 3 weeks.
FAQ
Why September 22? The autumnal equinox in the Northern Hemisphere usually falls on September 22 or 23. We use September 22 as a consistent reference point.
What if September 22 is today? The result is 0 days — fall begins today.
Does this work for the Southern Hemisphere? The same date marks the start of spring south of the equator, so the day count is identical but the season label differs.
