Longest Day of the Year

Even though it is quite a common phenomenon, not many people must be aware of the fact that there is something like the longest day of the year and the shortest day of the year on this planet. Technically speaking, a 'day' is the period of 24 hours wherein the Earth completes a single rotation. Colloquially, however, the term 'day' is used to refer to the period between the sunrise and sunset, when it is bright outside. Similarly, the term 'night' is used to refer to the period between the sunset and sunrise, when it is dark outside. Basically, days and nights are caused due to the rotation of the Earth. At one point of time, the Earth reaches a position wherein it is either inclined towards or away from the Sun, an astronomical event referred to as solstice, a term more familiar to geography students.

What is a Solstice and When does it Occur?

Solstice takes place twice in a year - once when the tilt of the Earth's axis is inclined towards the Sun, and once when the tilt is inclined away from the Sun. The former is referred to as the summer solstice, while the later is known as the winter solstice. This phenomenon and the position of the Sun in the sky enables the sunrays to reach the northern or southern extreme, owing to which the duration of the day either increases or decreases. Even though the term solstice technically refers to the exact moment wherein the phenomenon occurs, it is colloquially used to refer to the date on which the particular phenomenon occurs. The summer solstice occurs when the tilt of the Earth's axis is inclined towards the Sun at an angle of 23° 26'. As opposed to this, the winter solstice occurs when the Earth's axis is inclined away from the Sun at the same angle. The day on which the summer solstice occurs happens to be the longest day, while the day on which the winter solstice occurs happens to be the shortest day of the calendar year.

Which Day is the Longest Day in a Year?

Summer solstice occurs on the 21st June, which makes this day the longest day on the planet. Even though the phenomenon is restricted to a few seconds, this date is informally referred to as the 'summer solstice'. This day is marked by the longest period of daylight on the planet, except for the polar regions, where it is dark for half of the year and bright for the other half. As the Earth continues to rotate on its axis, one side of the same is exposed to the Sun for a longer duration depending on the position of the planet in its orbit. In the month of June, the northern hemisphere is tilted towards the Sun, and in December, the southern hemisphere is tilted towards the Sun. This continues as the alignment changes year after year.

As the alignment is gradual, one can witness the duration of the day increasing as we close in on June and then start decreasing. On June 21st the length of the day is at its peak, which again differs place to place. The places located at higher altitudes will experience a longer period of sunlight as opposed to the places located at the lower altitudes. In fact, some places, such as the Scandinavia, even go on to witness a strange phenomenon referred to as the mid-night Sun, owing to the long hours of sunlight. As the duration of the day increases during the summer solstice, the duration of the night decreases. During the winter solstice, which is the shortest day of the year, the days are shorter, while the nights are longer.

Though rarely, this phenomenon which usually occurs on the 21st June can also occur on 20th June or 22nd June. In 2008, summer solstice occurred on 20th June at 23:59 hrs. This was only the second time since 1975 when this phenomenon didn't occur on 21st June. In 1975, it occurred on 22nd June, an occurrence which will be repeated again only in 2203. Being the longest day of the year, it also has a great significance in various cultures, where it is celebrated in the form of rituals, festivals and even gatherings, such as midsummer parties.