Suave is a simple web development F# library providing a lightweight web server and a set of combinators to manipulate route flow and task composition.
The header value wasn't in GMT (It was the time on the current server timezone with 'GMT' written after)
On filesystems with millisecond precision times in fstat a 304 was never returned as the header value is only precise to the second. (All recent linux FS and windows NTFS are in this case)
Last accessed time was used instead of last modified