How to set Creation date for file...

[momesana]

The same applies to uptime

Without modifying the kernel sources?

[wysota]

Without modifying the kernel sources?

Of course. Never underestimate the power of the Dark Side

[marcel]

I think so. I think it could be done with a kernel module, but I don't exactly know how.
I'm looking for the uptime sources right now.
I believe it can be done if the kernel module will replace the functional part of the kernel that is used by uptime to report at least the uptime.

[wysota]

There are surely easier ways, but /proc/kcore and gdb are a crude/h4x0r way to do it too.