In the Earth's Northern Hemisphere—including Turkmenistan—nights will now be longer than days; astronomical autumn began on September 23 at 05:05 Ashgabat time. At that moment, the center of the Sun's visible disk crossed the celestial equator, moving from the Northern Hemisphere of the celestial sphere into the Southern Hemisphere.

The moment of this intersection is called an equinox and occurs twice a year—in the spring and autumn. From that point on, the night becomes longer than the day in the Earth's Northern Hemisphere, whereas in the Southern Hemisphere, conversely, astronomical spring begins and nights grow shorter.

The equinox equalizes the duration of day and night across virtually the entire planet: the Sun spends approximately 12 hours above the horizon and 12 hours below it. In reality, however, the period of daylight on September 23 will last slightly longer than 12 hours; due to the refraction of sunlight in Earth's atmosphere, an observer sees the sun rise earlier and set later than the luminary's actual position would dictate. A perfect balance between day and night will occur a few days after the equinox.

Astronomers note that while the exact moment of the equinox cannot be seen directly, certain accompanying phenomena are observable. For instance, the full moon rises earlier than usual during this period, and conditions become more favorable for viewing zodiacal light—a rare celestial phenomenon appearing as a faint, cone-shaped glow above the horizon—before dawn.

The autumn equinox in Turkmenistan coincides with the ongoing winter wheat sowing campaign, which began on September 3 across all the country's provinces.