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There's a workaround for that using Conditional Logic. Like if the user passes the 30 days limit, you can hide the submit button and display a text message so the user will be aware of the limit at the same time, they can't submit the form since the submit button is hidden.
To achieve that,
1. Add a Date/Time Field to your form and a message using Text Tool.
2. Set a Hide/Show Condition like the following.
today on the screen below means the current users date and then add 30 days so users that selects more 30 days starting the current date, they will not be able to submit the form.
Here's an example: http://form.jotformpro.com/form/41353919041956?
Hope this helps. Thanks!