The summer or June solstice, the longest day for the northern hemisphere, falls on Monday or Tuesday (June 20 or 21), depending on the part of the world you are in.

This year's solstice is special as it coincides with the full moon, a phenomenon christened the "Strawberry Moon" by early native American tribes.

Here are some quick facts about the summer solstice and the "strawberry moon".

1. Longest day of the year in the north

For many ancient cultures, the movement of the Sun is used to mark seasons and festivals. The June solstice is seen as the start of summer in the northern hemisphere, and the beginning of winter south of the equator.

It refers to when the Sun is directly overhead the Tropic of Cancer. This year, the precise moment it happens is at June 21, 6.35am Singapore time.

Days can get as long as about 17 hours in places like Britain, and 15 hours in Beijing. Places above the Arctic Circle, far north of the equator, have days of continuous sunlight.

Meanwhile, it is the shortest day of the year in the south, and Antarctica is shrouded in darkness.

2. Why there are solstices

The Earth is tilted at about 23.5 degrees as it orbits the Sun, which means that the northern hemisphere gets more sun in some months, like June, July and August when the North Pole is pointed towards the Sun.

The opposite is true south of the equator.

The summer solstice falls on the day that the North Pole is tipped the nearest to the Sun.

3. "Strawberry moon"

In the northern hemisphere, the June solstice coincides with the "strawberry moon" for the first time since 1967.

The "strawberry moon" is the name given to any full moon in June. Native Americans gave it this name as it marks the beginning of the strawberry season.

Because of the relative positions of the Sun and the Moon, the Moon takes on a rich, golden hue. It is also known as a "honeymoon".

While the strawberry moon is a common phenomenon, the next time it coincides with the summer solstice will be in 2062.

4. How about in the tropics?

In the tropics, the effect is much less pronounced. Singapore is about one degree north of the equator, and the difference in the length of the day will not be noticeable.

Said Mr Albert Ho, president of the Astronomical Society of Singapore: "The summer solstice is significant for places further north of the equator, for instance Taiwan, as the Sun is directly overhead.

As for the "strawberry moon", he added: "Full moon for Singapore was two days ago, there won't be any discernible difference for Singaporeans."

Every year, hundreds gather at the Stonehenge to see the summer solstice sunrise, which aligns perfectly with the stone circle on this day.

Many ancient monuments, such as the pyramids, were built so that the structures synced with the movements of the Sun.

In pagan tradition, the shortest night of the year has magical properties, and is when fairies can be seen. In New York city, a day-long yoga event is held, while in Sweden, it is a day of indulgence and revelry.

The Chinese celebrate duan wu jie or the dragon boat festival near the summer solstice. While the festival is said to commemorate the poet and minister Qu Yuan for his patriotism, traditions like racing dragon boats and eating dumplings appear to be pre-existing customs.

The Chinese city of Yulin holds a controversial annual festival on the summer solstice devoted to the consumption of dog meat.