This object reports how long the system clock has currently been in holdover mode, counting up in real time while the reference is lost and resetting to 0 once a valid reference is reacquired. Unlike the last-holdover object which is a historical record, this one is live; an admin can poll it repeatedly during an ongoing outage to see the holdover duration actively climbing, telling them the reference loss is still ongoing rather than already resolved. If this value keeps increasing across successive polls rather than resetting to 0, the device is still without a valid timing reference and its internal oscillator's drift is accumulating the whole time.