How do I delete files of a certain date?

My understanding is that you want to delete a certain uploaded file or attachments. Please take note that you need to delete the actual submission for the attachment to be deleted. Here's how:

In the Submissions page, you can filter the form submissions via the Time Frame option. Here's a screen capture:

After filtering it, look for the submission in the Grid Report and delete it.

Please check the complete guide here: https://www.jotform.com/help/377-How-to-Delete-Form-Submission-Data.

Hope that helps. Thank you.