Monotonic time is a measurement of the time the system has been actively running since boot. In accordance with this definition, it is set to zero when the kernel initializes the timer hardware early in boot, and does not include time spent in Suspend-To-Idle.
Monotonic time is the most reliable time standard on Fuchsia and reading monotonic time is usually cheaper than reading UTC or local time. Monotonic time is always available and it always increases continuously and monotonically. Monotonic time ticks at a rate determined by the the underlying hardware oscillator, and no attempts are made by Zircon to correct that rate against any external reference.
Since monotonic time counts from power on, it is only meaningful in the context of a single power cycle on a single Fuchsia device.
Components may read monotonic time using
zx_clock_get_monotonic.