Equinox in Hamlet

Some say that ever 'gainst that season comes
Wherein our Saviour's birth is celebrated,
The bird of dawning singeth all night long:
And then, they say, no spirit dares stir abroad;
The nights are wholesome; then no planets strike,
No fairy takes, nor witch hath power to charm,
So hallow'd and so gracious is the time.
(Hamlet, 1.1.173-179)

Compare Beckett on the equinox and on the second dark.