Absence enrollment seniority date

Hello,

We are experiencing a problem where absence enrollments are always defaulting to the first of the year. We have designed the plan so that enrollments should occur on the employees' seniority date. Employees should be accruing time off based on their length of service using the seniority date as the anniversary, with different accrual band rates for each year.

The accrual matrix is working as expected, and the enrollment start rule is set to "as of event". Basically the plan is working as expected in all other aspects except the enrollment date, which is defaulting to Jan 01 of the current year for all employees. I think we must be missing something obvious, but can't see what we've done wrong.