This section applies when we credit you with quarters of coverage (QCs) under §404.141 for calendar years before 1978 and under §404.143 for calendar years after 1977. We cannot credit you with a QC for—

(a) A calendar quarter that has not begun;

(b) A calendar quarter that begins after the quarter of your death;

(c) A calendar quarter that has already been counted as a QC; or

(d) A calendar quarter that is included in a period of disability established for you, unless—

(1) The quarter is the first or the last quarter of this period; or

(2) The period of disability is not taken into consideration (see §404.320(a)).