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The autumn equinox is today, Monday the 23rd of September, officially marking the astronomical beginning of fall in the Northern Hemisphere as day and night reach nearly equal length across the globe.
The equinox happens at 12:18 p.m. in Saskatchewan, when the sun crosses the celestial equator moving southward. This astronomical event signals the transition from summer to autumn, with daylight hours continuing to decrease until the winter solstice in December.
For us on the ground, looking up, this day has served as one of the natural dividers of the human year for millennia. It has associated festivals all around the world as harvest finishes and preparation for the winter season begins. Structures like Stonehenge were built to align with these astronomical events, demonstrating their historical significance for human societies.
From a planetary point of view, it has to do with the Earth's axis. An easy way to picture it is to imagine the planet either leaning toward or away from Sol — our Sun.
During the equinox, the Earth's axis tilts neither toward nor away from the sun, resulting in approximately 12 hours of daylight and 12 hours of darkness worldwide. The word "equinox" derives from Latin, meaning "equal night," though the phenomenon represents more than just balanced daylight. For locations in the Northern Hemisphere, the autumn equinox marks the sun's apparent "journey southward," leading to progressively shorter days and longer nights.
Two equinoxes occur annually — the spring equinox around March 20th and the autumn equinox around September 22nd or 23rd. These dates shift slightly each year due to Earth's orbital mechanics and the 365.25-day calendar year that necessitates leap years. There are also two solstices, which mark the longest and shortest days of the year. During solstices, one hemisphere experiences maximum daylight while the other faces minimum daylight. Equinoxes represent the midpoint between these extremes.
Events like these are not just symbolic: The autumn equinox triggers various natural phenomena. Many animals begin migration patterns, while deciduous trees start changing leaf colors as chlorophyll production decreases. Daylight reduction signals biological processes that prepare flora and fauna for winter conditions.
From Monday forward, Northern Hemisphere locations will experience increasingly shorter daylight hours until the winter solstice on December 21st, when daylight begins lengthening again. The opposite occurs in the Southern Hemisphere, where spring begins and daylight hours increase.
The equinox serves as a natural calendar marker, reminding us of Earth's constant motion and the cyclical nature of seasons. For Saskatchewan residents, the autumn equinox signals the approach of harvest season completion and preparation for winter weather patterns ahead — as it has for thousands of years.