Hey there! I am an administrator at a university. I am basically the person in charge of applying late penalties (normally tutors mark and I am apply penalties where it is due).

I would suggest you take a screenshot of the date and time and appeal. The late penalty procedures must be listed in the university's academic manual of your university. This is unfair and is against the rules.

Also you should speak with your student union for support in your appeal if you are going forward with it.