This is a comment on If-Modified-Since header does not works, posted by WikiAdmin at 12.06.2019 07:46

View source for 304 code response delay

In the ##run## function there is the following line
%%
if (!$user && $this->page['modified'])
{
	header('Last-Modified: ' . Ut::http_date(strtotime($this->page['modified']) + 120));
}
%%

which causes the 304 code response delay, I'm currently not sure which purpose that delay serves exactly.