The Autumn Equinox in Mexico: The Serpent That Crawls Down the Pyramid at Chichén Itzá
The 2026 autumn equinox (00:05 UTC on 23 September, 08:04:56 Beijing time) lands on the evening of 22 September in Mexico. Around sunset, seven inverted-triangle patches of light surface on the north staircase of the Kukulcán Pyramid at Chichén Itzá and join into a serpent crawling downward. This article looks at how the phenomenon is calculated, and at what locals are doing these days.