Astronomical and calendar first day of spring: between 19 and 21 March
For astronomers, and therefore also by the calendar, spring begins with the spring equinox.
This takes place when the sun - as seen from the Earth - crosses the celestial equator from south to north, which happens every year between 19 and 21 March.
On average, there are 365 days, 5 hours and 49 minutes between two first days of spring, which means that each one starts slightly less
than 6 hours later than the previous one.
By the time 4 years have passed, the time has therefore shifted by 23 hours and 16 minutes.
Fortunately, there is then always a leap year, which not only absorbs this difference but actually overcompensates for it with the additional day in February.
Either way: flowers are always beautiful - especially at the beginning of spring!