"at" jobs are one-shot cron-like commands
<http://unixhelp.ed.ac.uk/CGI/man-cgi?at>
I can see how to do a cron-like job, but I see nothing in launchd that lets me run something once at a given date-time.
“Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.”
Bill Waterson (Calvin & Hobbes)