There are times you mean to create a page, prepare it, but not make it visible to site visitors till the right time. These are the two solutions:
Solution 1: Simply go to Page Properties: Custom Attributes, select Exclude From Nav, Exclude From Page List, and Exclude From Search Index attributes and check Yes. This will remove every link to your newly added page, so no clue at the front-end, this page already exists. This will do the job for most cases.
Solution2: If you create an important page, you want to hide it before the launch day, you can play with the permissions. Go to Page Permission and uncheck Guest & you are done.