Day and night will be almost of equal length on March 20, 2021, which is one of only two occasions in every year.
The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) explained that vernal equinox is an astronomical event that marks the start of spring in the northern hemisphere and autumn in the southern hemisphere.
"The Sun's motion allows it to pass the First Point of Aries, known as vernal equinox, an imaginary location in the sky defined in our coordinate system as a place where the ecliptic and the celestial equator meet. It marks the zero point of the Right Ascension grid, the celestial equivalent of longitude on Earth," PAGASA said.
"Due to the wobbling motion of the Earth known as precession, the First Point of Aries now lies in Pisces. The Sun reaches this point on March 20 at 6:00 p.m. (Philippine standard time), marking the beginning of spring in the northern hemisphere and autumn in the southern hemisphere," it added.
The Philippines is above the equator and part of the northern hemisphere. Although there is no spring season in the country, warm and dry season prevails from March until May.
On the day of the vernal equinox, PAGASA said "night and day are about the same length on the same latitude in both hemispheres."
Days will begin to last a little longer and nights get a bit shorter in the country after the vernal equinox.
Every year, equal lengths of day and night happen twice a year during the vernal and autumnal equinox, in March and September, respectively.