"time and time over" meaning
Solution 1:
It is synonymous with time and time again, meaning that they came (to) wake us repeatedly:
over
5b : once more : again
Solution 2:
The meaning is more obvious if the quote is taken in context. The first four lines of Days, by Philip Larkin are:
What are days for?
Days are where we live.
They come, they wake us
Time and time over.
Plainly, the third line's "They come" refers to the series of days we live, day after day. "They wake us / Time and time over" refers to people waking, morning after morning; it is stated as if mornings actively awaken us.