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Unfortunately, we do not have that kind of feature, but you can check this workaround that I have here in this thread: http://www.jotform.com/answers/482561.
So basically, we have a datetime field that gets the users current date and time, we will then use the "Conditions" to show the form fields, including the submit button, only after a specific date.
If you have questions on the workaround that I have in the other thread, you can just reply here so that we can better assist you.
I hope that works.