Well, It Depends.
If we ask the Spanish Navy, they’ll tell you summer starts June 20 at 22:34.
But if you ask the Astronomical Office of the IGN, they tell you it’s June 21 at 0:34.
So….. it depends whether you’re at sea or not?
Summer is marked when the Earth reaches a certain point in its orbit around the sun. It doesn’t matter where you are on the planet, the body reaches that point at a certain time and it’s suddenly summer. It’s just an international agreement that astronomers agreed.
What does matter is how you measure time. So if, like the Spanish Navy, you’re on UTC (coordinated universal time) then summer apppears to start tonight.
But if you’re on Spanish time, GMT+1, then summer appears to start tomorrow. Because Spanish time is 2 hours ahead of UTC. And the UK appears to get an extra day of summer (not that they’ll notice).
But it doesn’t matter whether you’re on board a ship in the Med or in Madrid – summer will really start at exactly the same time.
Very, very early tomorrow morning.
And that’s why people got confused this year. By the way, the solstice is tomorrow (Tuesday), and it’s the longest day of the year.
In 2016, a full Moon, also commonly known as Strawberry Moon, will coincide with the June Solstice. The 2 events haven’t occurred on the same day since 1967 and will not coincide again until 2062. Exciting, isn’t it?