501.1. A dividend referred to in section 501 is a dividend on a share that is outstanding on 31 March 1977 of a prescribed series of tax-deferred preferred shares of a class of the capital stock of a public corporation, where that dividend becomes payable by the corporation after 1978 and, according to the case that applies to that series, not later than,(a) where the holder of each share of that series was entitled, under the terms and conditions in force on 31 March 1977 of those shares, to exchange it after a particular date for a share of another series or class of preferred shares of the capital stock of the corporation, that particular date;
(b) where the corporation was required, under the terms and conditions in force on 31 March 1977 of the shares of that series, to offer to purchase from all of the holders of those shares, no later than a particular date, all of the shares of that series, that particular date; or
(c) in any other, 1 October 1991.