My question involves a roommate in the State of: Illinois

I moved in with my room mate at his apartment and made a verbal agreement with him to pay rent to him in arrears on a monthly basis on the 1st of each month. He did not put me on the lease. When he decided to leave the apartment he gave me a date (mid-month) that he wanted me to leave by. He gave me this date verbally, and I was not given any written notice. I left the apartment before this date, and paid him rent for up to my move out date. However, he claims I owe him rent for the full final month, even though he told me I had to move out before the end of this month, and is threatening legal action.

I don't believe I owe him any rent for the remainder of the month. Am I correct?