The Talmud (Pesachim 93a) poses a question as to the nature of Pesach Sheini, when those who were unable to participate in the korban Pesach at its appropriate time have the opportunity to make up the obligation. The inquiry is whether this consititutes an independent festival, or an extension of the first Pesach that serves as a makeup. Those affected by the question, the Talmud notes, includes a convert who becomes Jewish in between the two occasions, or a minor who reaches adulthood during that time, both of whom were exempt from mitzvot during the first Pesach. However, this question is posed as well in the Sifre (B’ha’alotekha, 13), where only the case of the convert is mentioned as a possible ramification, and not that of the minor. The Netziv, in his commentary to the Sifre, explains that this actually represents a third view, to distinguish between the case of the convert and that of the minor. The convert was not Jewish during the first Pesach and thus was completely removed from obligation. The child, however, was included as a Jew in the obligation, enough so to impose a responsibility to bring the korban when it became possible, on the 14th of Iyyar. As R. Herschel Schachter (Eretz HaTzvi, 83) notes, this type of structure is relevant also to a child who becomes an adult in the middle of the thirty-day period of mourning. The Rosh (end of Massekhet Moed Katan) quotes the Maharam Rotenberg as obligating full mourning practices under the category of “sh’muah k’rovah” (one who hears of the death of a relative within thirty days of the event). The Rosh himself disagrees with this ruling Apparently, the Maharam Rotenberg’s reasoning is as above: the end of the burial, which begins the shivah period, applied to the child as well, but didn’t take effect until he achieved majority. R. Schachter discusses other aspects of the theory throughout that essay, including another example from this daf (93b). The definition of one who is considered “far away” for the purposes of korban Pesach is determioned based on one who is too far to walk, starting after sunrise, getting to Yerushalayim on time. Thus, even though the actual time for the mitzvah is not until chatzot, the period establishing the obligation begins earlier. (See also B’Ikvei HaTzon, p. 121.)