Vernal Equinox 2024 Time. In other words, on the day of the vernal. The vernal equinox marks the beginning of astronomical spring, while the autumnal equinox marks the beginning of autumn.

It is also the point in the calendar where the day length is more or less. For the model e ar5 simulations, all years have exactly 365 days and vernal equinox always occurs on march 21, hour 0.