A day is the time required -- 24 hours -- for the earth to make one complete revolution on its axis.
(A day; is; the time required -- 24 hours -- for the earth to make one complete revolution on its axis) (the earth; to make; one complete revolution on its axis)
A day the earth
is to make
the time required -- 24 hours -- for the earth to make one complete revolution on its axis
one complete revolution on its axis