FF for Eligibility based on SENIORITY DATE

Hello experts,

We are trying to develop a Fast Formula on eligibility. The eligibility determines the worker eligible for compensation plan. The logic is that if the employee's seniority date is later than 31/08 of the previous year, then the employee would not be eligible. Anyway we got this error when compiling it:

" line 2, conflicting type usage"

Can you help us fixing it?

DEFAULT FOR CMP_IV_ASSIGNMENT_ID IS 0
DEFAULT FOR PER_SENDT_F_V3_SENIORITY_DATE IS '1901/01/01 00:00:00' (date)
DEFAULT FOR CMP_ASSIGNMENT_SALARY_DATE_TO IS '4712/12/31' (date)
DEFAULT FOR CMP_IV_PLAN_START_DATE IS '1951/01/01' (date)