on reserves.expirationdate's mysql format is date, however I think it could be datetime I have identified that many koha's librries are cataloguing pc's, study rooms as in-ite loans, the students may hold this kind of material, but the hold expiration date is suitable for books, but not suitable at all for in-site loans. It should be great if we could define expiration days for home-loans and expiration hour for in-site loans It should be also great if we could define close hours to do not assign a date_due beyond the close date