Section 407.15 - General enrollment period(a) Except as specified in paragraph (b) of this section, the general enrollment period is January through March of each calendar year.(b) An unlimited general enrollment period existed between April 1 and September 30, 1981. Any eligible individual whose initial enrollment period had ended, or whose previous period of entitlement had terminated, could have enrolled or reenrolled during any month of that 6-month period.