[LukeShu]

timesyncd also does this for "large offsets", but what "large" is is neither configurable nor documented, but in the source:

    /*
     * Maximum delta in seconds which the system clock is gradually adjusted
     * (slewed) to approach the network time. Deltas larger that this are set by
     * letting the system time jump. The kernel's limit for adjtime is 0.5s.
     */
    #define NTP_MAX_ADJUST                  0.4

[fao_]

> neither configurable nor documented, but in the source:

Build it yourself and pass -DNTP_MAX_ADJUST=XX