Eleven Months, Not Twelve, and Why

Mourning for a parent is singled out for a longer period than mourning for any other relative because Jewish law treats the obligation to honor one's father and mother as a distinct and especially weighty commandment, which is why shloshim's thirty days apply as the full mourning period for a spouse, sibling, or child, while a parent's loss extends the milder restrictions across a full twelve months. Kaddish, the mourner's prayer recited for a parent across that year, is nonetheless traditionally stopped after eleven months rather than continued through the twelfth, a deliberate gap explained in most sources by reference to an old teaching that describes the standard period of postmortem judgment for the wicked as lasting twelve months, so that reciting Kaddish for the full year for one's own parent would carry the unwelcome implication that the parent belonged among those requiring the maximum term of judgment; stopping one month short is understood as a filial statement of confidence rather than a reduction of respect.

Shloshim itself allows a mourner to return to work and ordinary responsibilities while still withholding participation in celebrations, live music, and haircutting, a middle tier of restriction between the near total withdrawal of shiva and the eventual full return to ordinary life, and for relatives other than a parent this thirty day period is where formal mourning practice ends entirely rather than tapering further.