In the northern hemisphere, the longest day of the year (near June 22) when the Sun is farthest north. In the southern hemisphere, winter and summer solstices are exchanged. The summer solstice marks the first day of the season of summer. The declination of the Sun on the (northern) summer solstice is known as the tropic of cancer (23° 27′).
http://scienceworld.wolfram.com/astronomy/SummerSolstice.html
see http://cantonbecker.com/retrograde for details…
Bring your sunglasses this year! The peak of the Perseids (100 meteors per hour) happens smack dab on the full moon, so you might have to squint to see any trails…
The date (in the northern hemisphere) when night and day are nearly of the same length and Sun crosses the celestial equator (i.e., declination 0) moving southward (in the northern hemisphere).
http://scienceworld.wolfram.com/astronomy/AutumnalEquinox.html