My Mac application, MailSteward , has always had a feature allowing the user to schedule the app to archive their email in a database. To do this MailSteward uses an old standby in the UNIX system, called crontab, which has been around since the beginning of time, i.e., the creation of UNIX.
Now, running the beta of Mojave, MacOS 10.14, it doesn’t work anymore. So I am switching over to launchd, the Apple system for scheduling daemons and agents. What a nightmare! The crontab is simple and elegant. Launchd is incredibly complicated and has some of the worst documentation I have ever seen.
If you google something like “macOS cocoa schedule application with launchd”, you will get a list of links to very frustrated developers. I never was able to find a clear explanation of how the Hell to do it. There were a few quite confident how tos, but they used old commands that Apple has since deprecated and which don’t work anymore.