Function is_synchronised 

pub fn is_synchronised() -> Option<bool>

Whether this device’s clock is synchronised with a time source, when the platform can say: Some(true) synchronised, Some(false) known not to be, None when nothing here knows. A device whose clock is minutes out produces codes nothing accepts, and the machine is the only place that can tell.

It answers for the platform, not for a feature: every surface that shows time-sensitive data asks the same question.