The cron scheduler has been made more robust against changes in the system clock (caused by e.g. DST changes, NTP syncs or manual setting). A more granular management for cronjob events has been introduced, now supporting a `TIME_SYNC` event besides the usual `STOP`. When the cron scheduler detects a system clock drift (i.e. the timestamp offset before and after a blocking wait is >1 sec) then all the cronjobs are notified and forced to refresh their state.