How can I automatically delete records from a table when today's date is say 30 days after the records' creation?

Re: "How can I automatically ...",

No problem, use an aptly named feature called "Automations".  Very recently they were improved to be able to run an a scheduled basis.  So they can run every day or every week to delete records meeting a certain criteria.

Here is some help on Automations.  https://help.quickbase.com/user-assistance/cs/cs_about_automations.html

It seems you can only do automations based on numeric data types, so I just created a numeric formula that was 1 if the file is >30 days old and 0 otherwise, and then set the automation to run off that field as opposed to the date field.