Today was the summer solstice–the year’s longest daylight period. Additionally, this particular day is the “earliest” to occur on the calendar since the days of George Washington in 1796. This calendar oddity is not a true physical phenomenon but rather an embedded inaccuracy in how we measure time. A complete day is not precisely 24 hours.
As a result, we have “leap years” and “leap seconds” and such nonsense to account for this imprecision. The accumulation of these “leaps” results in the solstice not occurring on the same calendar day. This year the solstice falls on June 20. In other years, it may fall on June 21 or June 22. Fun little tid bit!
https://www.washingtonpost.com/weather/2024/06/19/summer-solstice-longest-day-earliest