module Sntp: Sntpval query : ?timeout:Core.Time.Span.t ->
       ?port:int ->
       string ->
       [ `Error of Core.Exn.t | `Offset of Core.Time.Span.t | `Timeout ]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.