June solstice

The June solstice is the moment each year when the Sun reaches its greatest northern declination, marking the start of astronomical summer in the Northern Hemisphere and winter in the Southern Hemisphere.

Earth's axial tilt: Earth’s rotational axis is tilted about 23.4 degrees relative to the perpendicular to its orbital plane. This tilt directs the Northern Hemisphere toward the Sun at the June solstice.
Astronomical season: An astronomical season is one of four annual periods defined by solstices and equinoxes. The June solstice marks summer’s start in the north and winter’s in the south.
Tropical year: A tropical year is the interval between successive passages of the Sun through the vernal equinox. Its relation to the equinoxes and solstices underlies the seasonal calendar.
December solstice: The December solstice is the moment each year when the Sun reaches its greatest southern declination. It is the opposite annual extreme, bringing opposite seasons in the two hemispheres.
Time zone: A time zone is a region that uses the same standard time, usually defined by an offset from Coordinated Universal Time. The solstice can fall on different calendar dates in different time zones.
Ecliptic: The ecliptic is the apparent annual path of the Sun against the background stars, corresponding to Earth’s orbital plane. The Sun reaches its northernmost position relative to the celestial equator along this path.
Midnight sun: The midnight sun is a period when the Sun remains above the horizon at local midnight in polar regions. It occurs north of the Arctic Circle around the June solstice.
Gregorian calendar: The Gregorian calendar is the civil calendar introduced by Pope Gregory XIII in 1582 and used internationally today. Its leap-year rules keep June solstice dates near the same calendar days.
March equinox: The March equinox is the moment when the Sun crosses the celestial equator moving northward. Unlike the June solstice, it occurs when neither hemisphere is tilted maximally toward the Sun.
Sunrise: Sunrise is the daily event when the Sun’s upper edge appears above the horizon. Atmospheric refraction and local horizons affect solstice sunrise observations.

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