Yosef Karo, Shulchan Aruch — Yoreh Deah 396
“ A mourner that did not perform his mourning within seven (days) , whether accidentally or purposefully, fulfills it (the mourning) for all of the thirty, aside from the tearing. That if he did not tear during the time of his warmth (his raw emotion) , he may tear only within seven (days) , except for his father and mother, for whom he tears even after seven. ”
