-/* Fills struct timeval with time since EPOCH from real-time clock (i.e. wall-clock).
- * - Hibernation/suspend time is included
- * - adjtime()/NTP adjustments affect this clock
- * Return 0 on succes, -1 else with errno set appropriately.
+/*
+ * Three clocks are available (cf. man 3 clock_gettime):
+ *
+ * REALTIME clock (i.e. wall-clock):
+ * This clock is affected by discontinuous jumps in the system time
+ * (e.g., if the system administrator manually changes the clock), and by the incremental adjustments performed by adjtime(3) and NTP.
+ *
+ * MONOTONIC clock
+ * Clock that cannot be set and represents monotonic time since some unspecified starting point.
+ * This clock is not affected by discontinuous jumps in the system time
+ * (e.g., if the system administrator manually changes the clock), but is affected by the incremental adjustments performed by adjtime(3) and NTP.
+ * If not available on the system, this clock falls back to REALTIME clock.
+ *
+ * BOOTTIME clock
+ * Identical to CLOCK_MONOTONIC, except it also includes any time that the system is suspended.
+ * This allows applications to get a suspend-aware monotonic clock without having to deal with the complications of CLOCK_REALTIME,
+ * which may have discontinuities if the time is changed using settimeofday(2).
+ * If not available on the system, this clock falls back to MONOTONIC clock.
+ *
+ * All now_*_timeval() functions fill the `struct timeval` with the time from the appropriate clock.
+ * Those functions return 0 on success, -1 else with errno set appropriately.
+ *
+ * All now_*_sec() functions return the time in seconds from the approriate clock, or 0 on error.
+ * All now_*_usec() functions return the time in microseconds from the approriate clock, or 0 on error.