Is it possible to add last-modified without a backend?

Question

Web development

There is some large system written in java. SEO team asks to add if-since-modified.
Adding / changing it is very expensive for such a small task. Here the back wants to know if it is possible to do this somehow from the front only. Adding the last-modified meta info header to the header does nothing.
Tell people in the know, please. Maybe I'm asking stupid.

Answer 1

As a knowledgeable person, I suggest: And drive your bek into the cold, he is incompetent.