daily logfile rotation: example C code

[Jacob Yocom-Piatt]

there is data coming over a UDP broadcast every second that i would like 
to log to a file that rotates each day. writing the data to a file as it 
comes in is easy enough but i believe that the time-based rotation is 
replicated in many existing applications.

could someone please refer me to a good example of C code that does 
time-based log rotation? i see no need to reinvent the wheel and 
examples from openbsd source are preferred for educational purposes.

cheers,
jake