Dear John-Maxwell Samuel,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
We went through your post carefully and understand that you are trying to block edits in SharePoint list after the day has passed.
As per the search and test on our side, we're afraid that there' no out of box way to achieve this in SharePoint currently, sorry for the inconvenience caused.
If you are willing, to check if there is any customized way to achieve this, we'd recommend you post this question to Microsoft Q&A Community with SharePoint Development tag or Microsoft Power Platform Community Forum, to check if Power Platform can help. Members and engineers over there will focus on the specific situation on your side and share suggestions for you.
Apologies for redirecting you to different community as the members in the category posted focus on the users with out of the box concerns on SharePoint, and have limited knowledge on the customized solutions; so to get the fast and better assistance, we have redirected you in the correct path.
At the same time, we will also keep this thread open, so other Community members and Experts can also share their suggestions and inputs.
Appreciate your patience and understanding. Have a great day!!
Sincerely,
Rhoda | Microsoft Community Moderator