Overview
- The Servicio de Hidrografía Naval, which published the official bulletin on Tuesday, confirmed the 2026 vernal equinox will occur on 22 September at 21:05 Hora Oficial Argentina, corresponding to 00:05 UTC.
- An equinox is the instant the Sun crosses the Earth’s equator so daylight and night are roughly equal, and September’s event marks spring in the Southern Hemisphere and autumn in the Northern Hemisphere.
- SHN explained the date shifts each year because the tropical year is about 365.2422 days while the Gregorian calendar averages 365.2425 days, producing small timing differences that accumulate over centuries.
- Popular celebrations in Argentina that mark spring on 21 September do not always match the astronomical start of the season, which can fall on the 20th, 21st, 22nd, or rarely the 23rd.
- SHN noted that only after a roughly 400-year cycle do the calendar dates and the tropical year realign, so the official equinox timing will continue to vary year to year.