One of the best things about summer are the extra hours of daylight, and the most daylight you'll get is during the summer solstice.

Although summer is just getting started, the days will start to get shorter from here on out. The next thing you know, you'll be trading in your sunblock and shorts for scarves and hand warmers. But let's not get ahead of ourselves. Here's a look at some interesting facts about the unofficial first day of summer.

It happens on different dates

The summer solstice happens between June 20 and June 22, depending on the year and your time zone. In 2016, the solstice falls on June 20 at 6:34 p.m. EDT.

It's the longest day of the year (kind of)

Technically, it's not the longest day of the year because all days have the same number of hours, but the summer solstice is the day of the year with the most hours of sunlight. As the Old Farmer's Almanac points out, the opposite happens with the winter solstice: "The sun is at its southernmost point and is low in the sky. Its rays hit the Northern Hemisphere at an oblique angle, creating the feeble winter sunlight."

It's technically just a moment

The moment of summer solstice is when the sun is directly overhead the Tropic of Cancer at noon. Way back when, the Tropic of Cancer got its name because the sun appeared in the constellation Cancer, Discover magazine reports. However, because of the shifting of Earth's axis, the Tropic of Cancer now has the wrong name. In 2016, during the summer solstice, the sun will appear\ in the constellation Taurus.

It's the first day of summer ... or not

The summer solstice may or may not kick off the summer, depending on who you ask. In meteorology, summer begins on June 1. But astronomers believe the summer solstice marks the start of the season. It all depends on whether you want to look at it in terms of meteorological seasons or astronomical seasons. Meteorological seasons are based on the annual temperature cycle, explains NOAA, while astronomical seasons are based on the position of the Earth relative to the sun.

summer solstice at Stonehenge Thousands gathered at Stonehenge in 2014 to witness the sun rising on the longest day of the year. (Photo: Paul Townsend/flickr)

It's a big deal at Stonehenge

There have been many theories why the prehistoric monument was built, but the interpretation that's most generally accepted is that Stonehenge was a temple aligned with the movements of the sun, reports English Heritage. Thousands of people gather at the structure, sometimes dressed in Druid attire, to mark the moment in June of summer solstice.

Other planets have solstices too

In fact, in 2016 Mars and Earth have solstices that fall within a few days of each other.

It's the longest day, but not the hottest day

Even though we get the most hours of sunlight on the summer solstice, it's not the hottest day of the year. Those are still typically weeks away. The Old Farmer's Almanac explains it this way:

At the summer solstice, the Northern Hemisphere receives the most energy (highest intensity) from the sun due to the angle of sunlight and day length. However, the land and oceans are still relatively cool, due to spring’s temperatures, so the maximum heating effect on air temperature is not felt just yet. Eventually, the land and, especially, oceans will release stored heat from the summer solstice back into the atmosphere. This usually results in the year’s hottest temperatures appearing in late July, August, or later, depending on latitude and other factors. This effect is called seasonal temperature lag.

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.