Simple Network Time Protocol
val query : ?timeout:Core.Time.Span.t ‑> ?port:int ‑> string ‑> [ `Error of Core.Exn.t | `Timeout | `Offset of Core.Time.Span.t ]query hostname returns the difference between the clock on the
local host and the clock on the host specified by hostname.
If the remote host is down or not running an (S)NTP service this call will `Timeout. Other errors, including some classes of resolution or network will raise an exception, which will be returned as `Error.