AWS::Logs::LogGroup:

Properties: 
  RetentionInDays: "\"Integer,  Possible values are: 1, 3, 5, 7, 14, 30, 60, 90, 120, 150, 180, 365, 400, 545, 731, 1827, 3653. The number of days log events are kept in CloudWatch Logs. When a log event expires, CloudWatch Logs automatically deletes it.\""