Legal Question in Landlord & Tenant Law in Illinois

Without looking at the whole lease document, it's really impossible to say. For one thing, there should be a rent schedule, and that may clear things up especially if it only provides for rent through 12/12. That being said, if there is an "ambiguity" on the face of the document and the landlord drafted the lease, then any such ambiguity is supposed to be resolved, at least in case a lawsuit is brought, "against the drafter" (against the landlord). And if rent is scheduled only through 12/12, the ordinary understanding is that the lease is not really ambiguous but there is a typo, but it may depend on what your goal is. For example if you want to protect yourself against the landlord saying it goes through 12/13, you may want a clarifying document.