The beginning of summer is astronomically the summer solstice, which is today in Finland. It represents the moment when the Earth’s poles are maximally tilted toward the Sun.
To commemorate the longest day of the year! (It’s the opposite The solstice of December, This shows the longest night and the shortest day. )
Geographically, this means that the Sun is directly above the Tropic of Cancer in the Northern Hemisphere and the Sun’s path in the sky is the northernmost.
(The Tropic of Cancer passes through Mexico, North Africa, the Middle East, India and China.)
In southern Finland, a day is about 19 hours.
https://finlandtoday.fi/todays-the-longest-day-of-the-year/ Today is the longest day of the year | Finland today | English news