How to calculate Date Difference in MS Access Database using DateDiff function

i used this code and it works

SELECT PersData.PNO, PersData.RANK, PersData.Name, PersData.DOSEN, PersData.UNIT, PersData.APPOINTMENT,PersData.FROM, PersData.SPECI,PersData.COURSESTR,DateDiff('d', [PersData.FROM], Now()) / 30 AS TEN
FROM PersData