Summer Solstice. The day when the Earth is tilted towards the sun and we (northern hemisphere) get the day with the most day light. Midsummer.
If you are in the northern side of the Equator, hope your longest day is filled with summer!
And I wish you a peaceful and restful day on your longest night, if you are in the southern side of the Equator, with hope of more sunlight coming your way.