This depends on what you mean by NTP. If you are running the NTP time synchronization daemon (ntpd) with a reasonable configuration, then the time will never jump. The daemon continuously slews the system time toward actual time. It doesn't "run" at intervals: it queries its time sources at intervals simply to determine how much to slew the time. You will never see skipped time, nor will your time move backward in any detectible way.
The time will jump, however, if you are synchronizing via certain other means. For example, if you use a cron job to run
ntpd -q (which you shouldn't do unless you have a very good reason and understand the possibll dire consequences), then your system time could instantaneously and wildly change each time this runs. The time could also jump when you first start ntpd, depending on how you have it configured.
If the exact time that a cron job was supposed to run does not occur (is skipped) due to a time jump, then it simply will not run. It will run at the next interval for which it is scheduled.
If the exact time that a cron job was supposed to run occurs twice (the time jumps backward), then it will run both times.
To solve the cron problem, run ntpd as a service/daemon, thus ensuring that your time will never jump. If you manually jump the time, you will have to check all of your cron jobs to determine what did not run (or will run twice) and manually intervene.
Of course, the best solution is to solve the time problem. The cron problem is simply a symptom of the much more serious time jump issue, which can cause all sorts of problems beyond cron (logging, auditing, SELinux, etc...)