When was or will be literally the longest day ever?

Answer 1

The Earth's rotation is very gradually slowing; within the next several million years, the day will be 25 or 26 hours long. Eventually, the Earth's rotation will be slowed to one day per year, and the Earth will become tidally locked to the Sun. That will be about the time that the Sun dies anyway, so it isn't something that we'll need to worry about in THIS lifetime. It will be in a few billion years.

For us, the longest day is the Summer Solstice, which occurs on June 21 in the northern hemisphere or December 21 in the south. The precise date of the summer solstice can vary a day either way, depending on the cycle of leap years, but you can look it up on the U.S. Naval Observatory's web site at http://www.usno.navy.mil.

For the longest period of continual sunlight in this century, try going to Antarctica, where scientists at the South Pole Station experience a "day" that lasts six months from approximately September 21 to March 21.

Answer 2

The length of daylight depends on where you are on Earth and the time of year.

The most noticeable effect is in the polar regions.

Daylight there, in the summer, can last the full 24 hours.

So, the answer is 24 hours.

Answer 3

The summer solstice, which usually falls on June 21st, is the day with the longest period of daylight of the year. It is the day when the Earth's axial tilt is most inclined towards the sun.