What is the maximum period for a rental agreement?

Sir I am a tenant and given 1 month notice to my owner however as I couldn’t find a house I told him that I would extend my stay by 10 more days . After agreeing to this , he came back and charged me excess rent as per new tenancy which starts only after 12th day from my notice ended. My clarification can he charge as per his assumptions or is the agreement still valid and he could charge as per existing rent ? Does agreement expire by giving 1 month notice ?