BSD / POSIX

Time

sys/time.h
sys/timeb.h
sys/times.h
sys/timex.h
time.h

other BSD / POSIX topics: Types & conventions · Threads & scheduling · Memory & IPC · Strings & text · Atomics, byte order & libkern · Data structures · Events & kqueue · Files & directories · Processes & signals · Networking · Terminals · Audit (BSM) · Tracing & debugging · Misc