millisecond clocks and delays Sleep for a number of milliseconds Return current system clock as milliseconds. Note that this clock can jump backwards (if the system clock is changed) so is unsafe to use for timers and time offsets. Use zclock_mono for that instead. Return current monotonic clock in milliseconds. Use this when you compute time offsets. The monotonic clock is not affected by system changes and so will never be reset backwards, unlike a system clock. Return current monotonic clock in microseconds. Use this when you compute time offsets. The monotonic clock is not affected by system changes and so will never be reset backwards, unlike a system clock. Return formatted date/time as fresh string. Free using zstr_free().