system last boot, in C

i'm programming in C to output the time of the system's last boot (linux).

can't read from /var/log/ since i don't have permission.

halp plz.

i can go to /proc/uptime and read it from there

but is there a way for it to show the time in format of day hour:min:sec?

the btime in /proc/stat shows the seconds since 1/1/1970 till the time it was last booted, but thats not helping much..

=((