Can Absence Start Date or Absence End Date be used for Journeys event triggers?

Summary:

I would like to trigger a Journey based on a time after an Absence Start Date or before an Absence End Date

Content:

I have a requirement to trigger a Journey after 28 calendar days of sickness absence. The absence type unit of measure is working days so the existing Duration attribute cannot be used to determine when the Journey should be triggered as this would be different depending on the work pattern of the employee.

Ideally, I would like to use Absence Start Date as the attribute and when SYSDATE > START_DATE+28 for a sickness absence, the Journey would be triggered.