What is the Open Enrollment window?

Medicare Advantage and Part D: October 15^th through December 7^th. There is no annual enrollment period for Medicare Supplements

Medicare Supplement open enrollment is a six month period beginning the firs to of the month of the individual’s birth month and/or the effective date of their Medicare Part B.  For example: John Smith turns 65 August 3, 2017 but retires 12/31/2017.  If he chooses to enroll in Medicare Part B when he is first eligible on August 1^st, he will have one six month open enrollment window ending at the end of January in 2018.  If he decides to keep his group insurance until he retires and activates his Part B on January 1, 2018, then his open enrollment window runs from January through the end of June in 2018.