Is the 21st of June the longest day of the year?

Answer 1

The Summer Solstice, which is the longest day of the year, generally occurs on June 21 each year, but this can vary a day either way depending on the cycle of leap years. (This is actually the SHORTEST day of the year in the Southern Hemisphere.)

The reason is that the Earth spins on its axis, and the Earth also orbits the Sun. The orbital plane of the Earth's orbit is called the "ecliptic", and if the Earth's axis of rotation were "normal to" (meaning, at a 90 degree angle to) the ecliptic, then the Sun would always be over the equator and we would have no seasons - and the days and nights would always be 12 hours long.

But the axis of the Earth's rotation isn't normal to the ecliptic; it is tilted at about 23.4 degrees. This "axial tilt" gives us our seasons. On June 21, the northern hemisphere of the Earth is tilted toward the Sun, as close as it ever does; the next day, as the Earth orbits the Sun, it starts to move a bit away.

Answer 2

Yes, June 21st is typically the longest day of the year in the Northern Hemisphere and marks the summer solstice. This is when the Earth's axial tilt is most inclined towards the Sun, resulting in the longest period of daylight for the year.

Answer 3

In the northern hemisphere it is June 21st. In the southern hemisphere it is December 21st.