1000 seconds, I believe, is the max that ntpd will correct without manual intervention. It also usually corrects by slewing time, so that the time correction d

1000 seconds, I believe, is the max that ntpd will correct without manual intervention. It also usually corrects by slewing time, so that the time correction doesn’t upset timers so much. I believe it can take several weeks to correct for a large offset. That information is true for most linuxes, and may not have any direct bearing on iOS.