Answer:

night

Answer	Crossword Clue
NIGHT	When to stargaze
NIGHT	It never occurs above the Arctic Circle during the summer solstice
NIGHT	Prime-time time

NIGHT	When one sees stars
NIGHT	Busy time for bats
NIGHT	Time for vampires
NIGHT	Brief remark upon retiring
NIGHT	See 26-Across
NIGHT	Dark hours
NIGHT	Dracula's time
NIGHT	Dusk to dawn

NIGHT	Darkness
NIGHT	When most people retire
NIGHT	Time for some shifts