Fall officially began at 7:04 p.m. last Tuesday, September 22, 2026. This marked the point in the Earth’s orbit around the Sun when sunlight shone directly on the Equator. Day and night were also nearly equal on this date, though it wasn't an exact 50-50 split.

The true balance of day and night, referred to as the equilux, occurs a few days after the autumnal equinox. That fell on Saturday, September 26 this year, when Baton Rouge saw 12 hours and 40 seconds of daylight. Moving forward, nights become longer than days — at least until springtime.

The separation between equilux and equinox happens for a few reasons. Two factors contribute to the discrepancy:

Definition of Sunrise/Sunset: Sunrise is defined as the point when the Sun’s upper edge becomes visible above the horizon, whereas sunset occurs when the last sliver of the Sun sinks below the horizon. In other words, as long as any portion of the Sun is visible, it counts as daylight. This adds a few minutes of daylight each day. Specifically on the equinox, the choice in definition tips the balance toward more daytime than nighttime.

Atmospheric Refraction: Earth’s atmosphere bends, or refracts, sunlight, causing the Sun to appear slightly higher in the sky than its “true” position. This makes the Sun visible before it truly rises and after it actually sets. In other words, atmospheric refraction extends the time spent in daylight by several minutes.

These factors result in approximately eight minutes of extra daylight on the fall equinox. The same effects listed above add daylight during the spring (vernal) equinox as well. The spring equilux occurs a few days before the equinox.

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