If it were just linear like AWS (https://news.ycombinator.com/item?id=9567761 https://news.ycombinator.com/item?id=9567761), then an NTP client pointed to a sme

If it were just linear like AWS (https://news.ycombinator.com/item?id=9567761 https://news.ycombinator.com/item?id=9567761), then an NTP client pointed to a smearing NTP server will have an immediate 12ppm drift discontinuity (NTP continually models the hardware clock as a fast or slow clock with a linear drift from true time). Perhaps the NTP client’s control algorithm will bounce around as it tries to figure out the correct hardware clock drift, and perhaps this bounce is smoother when you use cos over a day. But I haven’t studied the NTP algorithm enough to tell for sure. Edit: from other comments here, it looks like Google also uses a linear smear now (a linear drift over 20 hours is 14ppm).