We have Jenkins jobs set to run overnight as they take hours to run. The last 2 days, the jobs kicked off as normal. The 3rd day, instead of running at 7pm-8pm (based on H in cron setting), the jobs started a full 12 hours later at 7am. 

The cron job looks like this:

H 19 * * 0-6

The time zone is set to America/Chicago in Jenkins and on the Linux server.