When Does Spring Start?
There are two answers to this question. In the meteorological calendar, spring begins on 1st March and ends on 31st May. In the astronomical calendar, spring starts on the day of the vernal (spring) equinox.
An equinox happens twice every year when the sun passes directly over the equator, making the hours of daylight and darkness roughly equal everywhere on Earth.
The vernal equinox marks the beginning of spring, and after it the days become longer and the nights shorter. The vernal equinox always occurs around 21st March in the Northern Hemisphere, and astronomical spring runs till 21st June 2021.
For more about the spring equinox and to try a wee quiz What is the Spring Equinox?