Almost 1,700 years ago, the vernal equinox was set for March 21 – but here in Sweden, the vernal equinox will occur on the twentieth of March for several years to come. So what actually controls the timing of the vernal equinox?
Vernal equinox means that day and night are roughly the same length – the word equinox is probably a contraction of day and night equinox. At the Council of Nicaea in the year 325, the vernal equinox was determined to be March 21, but the fact is that there is no fixed day for the vernal equinox.
Therefore, the timing varies
What happens during the vernal equinox is that the center of the sun crosses the celestial equator on its way north, while the autumnal equinox occurs when the center of the sun crosses the celestial equator on its way south. At these times, the day and night are about the same length.
Because we have different time zones on the globe – and because of the leap year cycle – the timing of the vernal equinox varies. Here in Sweden, for example, the vernal equinox will occur on the twentieth of March for many years to come, and in the leap year 2048 it will even fall on the nineteenth of March.
First Day of Spring
According to Swedish tradition, the vernal equinox is counted as the first day of spring, and in commoner society the day marked the start of spring farming – a busy period of ploughing, harrowing, fertilizing and sowing.
Like many other important times of the year, it was common to try to predict the future on this day. More precisely, on this day they tried to predict how the weather would be in the coming period, something that naturally had a great impact on the year’s harvest.
Spring equinox 2023
Monday, March 20, 2023 is the vernal equinox and the northern hemisphere officially enters a new season. The days are getting longer than the nights – and will be until September 23! Finally, we wave goodbye to winter and welcome spring, summer and sun.
Sources: ISOF, The Nordic Museum, SMHI
