.The Summer Solstice
is a day, but for astronomers, it's also a time. The 2022 June solstice occurred at 9:13 a.m. CUT. (Coordinated Universal Time is the same as Greenwich Mean Time.) This is when the Sun crossed the Tropic of Cancer.
And I should note that it's only northern summer solstice. The southern hemisphere had its winter solstice. Northern winter solstice occurs when the Sun crosses the Tropic of Cancer.
PS To be precise, the Sun, of course, isn't actually doing the moving. It's the Earth.