It's possible! But not Equinox-specific
In the Northern Hemisphere, people claim there are two days each year when you are supposedly able to balance an egg on its end: the vernal equinox and the autumnal equinox, otherwise known as the only days a year when the sun shines directly on the equator, and both night and day last for 12 hours. I thought this seemed fishy, so I set out to answer a few questions: Where in the world did this idea get its start? Is it possible to balance an egg anytime, or does it only work on the equinox? And could I do it? The short answers: China, we think. Yes and nope. And nope, not at all.
The origins of egg balancing are typically linked to Lichun, the beginning of spring in the Chinese calendar, which typically happens in early February. During this celebration, people balance fresh chicken eggs, likely celebrating the return to "balanced," mild weather, and spring's connection to fertility and rebirth. An article in a 1945 issue of Life magazine reported on the "egg-balancing craze" in Chungking, and it along with various follow-up articles are credited with kicking off the obsession in the States. However, to appeal to western audiences, the date to try to balance eggs was moved to the vernal equinox. The egg symbolism, of course, remains the same.
So, can you actually balance eggs? You can. But the equinox—and any other celestial happenings—have nothing to do with it. Rather, it's all about the shape and surface of the eggs. Despite first appearances, eggs aren't totally smooth. They're actually covered in bumps, dimples, and other irregularities that make it possible for some eggs to grip the surface they're on and balance. Others may not balance upright ever, and that's indicative of an uncooperative eggshell—or an impatient human.
Which leads me to my attempt to balance an egg, dear reader:
I'm blaming the egg.