This article explain what is the Reference Date that appear on the Recruiting Marketing jobs.
SuccessFactors Recruiting Marketing (RMK) - All Versions
The Reference Date in Recruiting Marketing (RMK) is used by public sites as the date displayed for a job. Subject to date rolling procedures.
It is not updated when the job is modified. It is the date the job was initially entered into the system or the last time the job was rolled. After the job ages past 28 days and is "rolled" the Reference Date field is updated with the date that the roll happened.
Recruiting Marketing was built to auto adjust the dates every 30 days. This was originally for security reasons, and also to increase conversions for candidates.
So the purposes of the rolling is to update the date every 28 or 30 days, so the candidates will see a “no very old” date there.
Reference Date Recruiting Marketing , KBA , LOD-SF-RMK , Recruiting Marketing , How To