Landlords can be required to return the security deposit or be subject to a large penalty. Often times states and or Cities have laws to protect tenants. You should contact a local lawyer.
Sometimes it depends how many units. We have had class actions against landlords for not paying interest on security deposits and not returning security deposits.
you need to contact a lawyer from the state you reside as each state has different law and each city can have different law.
Typically there is no language in these types of agreements which ultimately penalizes the landlord for returning your deposit later than agreed, unlike if you were late in your payments. An addendum is also likely not incorporated into the document, as it is crafted for his/her benefit. That being said, one might also look at the amount associated with this matter. For instance, one could easily argue in the absence of those terms, “business days” versus “total days”.
Were weekends and holidays factored? Presumably, you have already cashed the check which implies your acceptance. While you could file your issue in small claims court, there is a filing cost and of course your time which is also valuable in your consideration. All things to base your decision on whether you feel you have been made whole.