Can I publish automatically at a specific time?

When you say publish automatically at a specific time, do you mean that you wish your form to be enabled on a scheduled date? If so, unfortunately, it's not possible. Instead, what is possible is to disable the form on a scheduled date.

What I can recommend for this to be a possibility is add a script to show your form on your page if a specific date and time is reached, either coded in PHP or Javascript.

Here is a sample code in PHP:

<?php
$date = time();
$Showpage = strtotime('2017-07-30 00:00:00');
if ($date > $Showpage) {
?>

<iframe src="...">your jotform iframe code</iframe>

<?php
}
?>

For javascript, sample codes which you can use can be found on this thread from StackOverflow: https://stackoverflow.com/questions/13121448/show-hide-divs-based-on-date 

If you have additional questions, please let us know.