If the time differential is too extreme it will skip ahead or back instead of just skewing.<p>&gt; ...The ntpd algorithms discard sample offsets exceeding 128 ms, unless the interval during which no sample offset is less than 128 ms exceeds 900s. The first sample after that, no matter what the offset, steps the clock to the indicated time.<p>&gt; This may on occasion cause the clock to be set backwards if the local clock time is more than 128 [m]s in the future relative to the server. In some applications, this behavior may be unacceptable.