State weather bureau PAGASA said Thursday that day and night will be nearly equal in length worldwide on 20 March due to the vernal equinox.

According to PAGASA, this event marks the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. The Sun will shine directly over the equator, resulting in almost identical day and night durations across the globe.

“The March Equinox marks the start of spring in the Northern Hemisphere. On this day, the sun rises exactly in the east and sets exactly in the west,” PAGASA said.

PAGASA explained that astronomical seasons are determined by four key points in Earth's orbit: the equinoxes and solstices. These changes occur because Earth's axis is tilted at 23.5 degrees.

“As Earth moves around the Sun, different parts of the planet receive varying amounts of sunlight, leading to changes in temperature and daylight hours throughout the year,” the weather bureau added.

The vernal equinox occurs when the ecliptic — the Sun’s apparent path in the sky — crosses the celestial equator. This intersection point is known as the First Point of Aries. However, due to Earth's slow axial precession, this point is now situated in the constellation Pisces.

PAGASA emphasized that the equinox does not cause sudden weather changes but is part of Earth's consistent solar cycle. The event typically happens every year around 20 to 21March.