Answer: solstice

AnswerCrossword Clue
SOLSTICE

Start of summer or winter

SOLSTICE

Summer ..

SOLSTICE

Season-beginning phenomenon

SOLSTICE
First day of summer, e.g.
SOLSTICE
Equinox opposite
SOLSTICESummer .. (end of spring)
SOLSTICEFirst day of summer or winter
SOLSTICEJune 21-22 or December 21-22.
SOLSTICEPoint on the sun's ecliptic.
SOLSTICEWinter or summer time.
SOLSTICETurning point
SOLSTICESun's spot circa Dec. 22
SOLSTICEBiannual occurrence
SOLSTICEOne of two events a year
SOLSTICEA turning point
SOLSTICESemiannual occurrence
SOLSTICEFall follower
SOLSTICEOccurrence after the fall
SOLSTICEWinter begins with one
SOLSTICESummer starts with one
SOLSTICEJune event
SOLSTICESummer starter