The solstice on or about the 21st is the longest day of the year and the moment the northern hemisphere is tilted furthest towards the sun. In Shetland it barely gets dark at all around midsummer, a half-light locally called the simmer dim, and even in the south of England there is usable light well past ten in the evening.
June closes the second calendar quarter of 2027 on the 30th and marks the end of the third month of the tax year. Quarterly VAT returns, management accounts and half-year reporting all bunch into the last week of the month for businesses on a calendar-quarter cycle.
June 2027 runs to 30 days and closes the first half of a year of 365 days. Six months remain, carrying the summer holidays, the autumn clock change, both November commemorations and Christmas at the far end of them.