HTTP Header Problems

[eluser]adamfairholm[/eluser]
I'm using the CI header output class to send a last modified:

Code:

$this->output->set_header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");

However, when I check the headers its sending, I am getting the same date over and over again from 2 months ago. Any idea what could be causing this anywhere in Code Igniter or the server?

[eluser]adamfairholm[/eluser]
One thing I've noticed that may hold the key is that the Last Modified date on the Output class file is the SAME as the Last-Modified date that my headers are outputting. So I changed them all to normal header() php function headers but still the same thing. What's going on?

[eluser]adamfairholm[/eluser]
set_header is definitely taking the Last_Modified date from the index.php file's last modified date. I changed the last modified date of the file and it changed the headers. Any idea why this is going on?