I'm trying to create a sign-up form and post the link but not have it a

I'm trying to create a sign up form and post the link but not have it active until a specific date. Post it today (8/22) but not have the form "live" until September 1, for example.

You can manually disable it now. And enable it manually any time you like. Just go to the forms settings and toggle the form status.

The other alternative is to add a date field, set the date as current (date field properties), and use conditions to hide the submit button until a specified date.