From When Is Shloshim Counted—Death or Burial?
Question:
Is the thirty-day mourning period of Shloshim calculated from the time of death or from the time of burial?
Answer:
Shloshim, the thirty-day mourning period, is counted from the time of burial, not from the time of death. This is because the mourning process officially begins with Shiva, which starts at burial.
The laws of Shloshim begin immediately after Shiva ends—on the 7th day of Shiva after Shacharit—and continue for 23 more days, totaling 30 days from the burial. The final day of Shloshim (the 30th day) will always fall four weeks after the first day of Shiva, on the same weekday plus one. For example, if the burial and first day of Shiva were on a Monday, Shloshim will conclude on a Tuesday four weeks later.
Sources:
Rama 376:4 in name of Maharil regarding Kaddish; Shach 402:5 and 10 and Nekudos Hakesef 402 regarding a Shemua Kerova; See Taz 402:6 regarding Aveilus [Shiva/Shloshim] and 402:9 regarding the 12 months; Aruch Hashulchan 402:1 and 10; Nitei Gavriel 34:6; Vol. 2 1:2 that so rule all Poskim
