Code of Alabama
Article 1 - General Provisions.
Section 35-9-3 - Duration of Tenancy When Time for Termination Not Specified - Generally.

Where no time is specified for the termination of tenancy, the law construes it to be from December 1 to December 1 but if it is expressly a tenancy at will, then either party may terminate it at will, by 10 days' notice in writing.