The Lunar Month includes the time the earth has moved to get the to the same phase again not just one revolution around the earth.
However you may calculate it, we see the new crescent after 29 or 30 days. Not more or less: not less than 29 days, and not more than 30 days.
Because you've got a really old book that says so.
It may be old book, but it will teach you and correct your erroneous knowledge.
And even if it is old, the interpretation is new and recent, and it is also an inspiration and revelation.
it's all to do with perspective, isn't it? from our earthbound perspective (naked eye) it doesn't appear to revolve; but from any other perspective, anywhere but the Earth, like from another planet, the Sun or even the Moon itself, it does.
As I told them, and Dexter himself in his answer said, if you are outside the two objects: then of course you will see all sides of both objects .. logical.