How to reproduce

• Create a free style project
• Source Code Management - None
• Build Triggers - periodically - H/5 * * * *
  (The description below the input field indicates that it understands the cron syntax and matches by expectation)
• Build - Execute Windows Batch command - dir
• Save

Expectation - Job kicks off every 5 minutes
Observed - Job never kicks off.

Extra Info
The JOB only ever kicks off as expected (in next 5 min) only one time after Jenkins is restarted. Then onwards, it never kicks off. Going back to the configuration page, I see the following description under the cron configuration which indicates there is an issue. The time value it displays is not as expected.
"Would last have run at Thursday, 24 September 2015 11:05:11 AM EST; would next run at Thursday, 24 September 2015 11:05:11 AM EST."

Changing the cron config to something like H/10 * * * * updates the description correctly to match expected behaviour - except it does not kick off the job. Retuning back to the configuration page at a later time shows incorrect looking description.