John Kennedy actually said...
However, if the enlistment of a member of the Ready Reserve who is ordered to active duty under section 1 of this Executive Order would expire after February 28, 1963, but before he has served the entire period for which he was so ordered to active duty, his enlistment may be extended until the last day of that period.
Context
Executive Order 11058—Assigning Authority With Respect to Ordering Persons and Units in the Ready Reserve to Active Duty and...
10/22/1962