Shulchan Arukh, Yoreh De'ah 395

מקצת יום השבעה והשלשים ככולו. ובו ג' סעיפים:כיון שעמדו מנחמים מאצל האבל ביום שביעי מותר בכל דברים שאסור בהם תוך שבעה דמקצת היום ככולו לא שנא מקצת יום שביעי לא שנא מקצת יום שלשים כיון שהנץ החמה ביום שלשים בטלו ממנו גזרת שלשים (רא"ש ורבינו ירוחם): הגה ובמדינות אלו שאין המנחמין רגילין לבא ביום ז' צריך להמתין עד שעה שרגילין המנחמים לבא בשאר ימים דהיינו לאחר יציאה מבית הכנסת שרגילין לבא מנחמין כן נראה לי ודלא כמו שרגילין להמתין שעה על היום דאין הדבר תלוי רק בעמידת המנחמין (כן משמע באשיר"י):

As soon as the comforters have risen [to leave] from the presence of the mourner on the seventh day, he1The mourner. is permitted [to do] everything that he was forbidden during the seven [days of mourning], for part of the [seventh] day [is regarded] as the whole day,2M.K. 19b in accord with Abba Saul. also Pes. 4a; Nid. 33a, Rashi s.v. אין; supra § 393, 1 Gloss. Among the commentators there is a difference of opinion as to whether the principle ‘part of the day is regarded as the whole day’ (מקצת היום ככולו) refers only to the day or also to the preceding night (since the day is comprised of the preceding evening and the following morning until sunset. Gen. I, 5, ‘And there was evening and there was morning one day’). Tosaf. (M.K. 21b s.v. אפילו) and Asheri (to M.K. ibid.) maintain that this principle applies only to the day. N in T.H. holds that it refers to the preceding night as well. Caro as it may be seen rules in accordance with the first view, viz., that on the morning of the seventh day as soon as the comforters leave the mourner, the restrictions of the seven days become inoperative. However, in matters pertaining to the performance of a religiuos duty, e.g., Torah-study, marital intercourse we adopt the lenient view and consider part of the night of the seventh day as equivalent to the entire seventh day; in matters where no religious duty is involved, e.g., bathing, anointing etc. we rule that part of the seventh day following the night, is regarded as the whole day — P.Tesh. [and furthermore, there is] no difference whether it is part of the seventh day or part of the thirtieth day [of mourning],3M.K. 19b in accord with the Nehardeans. for as soon as the sun has risen on the thirtieth day, the restrictions of the thiry [days] cease to exist for him.4Asheri and R. Yeruḥam — G. On the thirtieth day when no comforters are present, the restrictions cease with sunrise — ShaK. Cf. Meg. 20a, Tosaf. s.v. ספירה. Gloss: And in these countries where it is not customary for the comforters to come on the seventh day, one is required to wait until the hour when it is customary for the comforters to come on other days, viz., after the departure [of the worshippers] from the Synagogue, [at which time] it is customary for comforters to come. Thus seems to me [to be the correct view], and not as the common practice is to wait an hour after the day [has commenced], for the matter depends solely upon the comforters rising [to depart].5Thus implied in Asheri — G.

שמע שמועה רחוקה בלילה כיון דסגי בשעה אחת סלקא אפילו בלילה:

One who heard [a death report of] distant tidings6 infra § 40 at night, — since one hour [of mourning] is sufficient [in such a case], it is accounted as valid even [if observed] at night.7Tur on the authority of R. Meir of Rothenberg and Asheri to M.K.

מי שמת אביו או אמו בראש חדש ניסן לא אמרינן בכ"ט באדר שאחריו מקצת היום ככולו אלא צריך לנהוג דברים האסורים בי"ב חדש עד שיכנס ראש חדש ניסן: הגה ונהגו להוסיף עוד היום שמת בו האב או האם לנהוג בו דין י"ב חדש ונכון הוא:

One whose father or mother died on the first day of the month of Nisan,8 Glos. — [the law is that] we do not say on the twenty-ninth day of Adar,8 Glos. following, 'A part of the day [is regarded] as the whole day,'9As in the case of the seven and the thirty days of mourning. For this principle applies only to days and not to months — TaZ, ShaK. RIDBaZ adopts a lenient view in this matter — P.Tesh. but one must observe those things that are prohibited during the twelve months [of mourning] until the first day of the month of Nisan8 Glos. arrives.10T. ha-Deshen s. 292. Gloss: It is also customary to include the day wherein [one's] father or mother died,11The anniversary of death or Yahrzeit even if it occurs on the Sabbath — ShaK. T. ha-Deshen (ibid.) states the reason as follows: Since on the Yahrzeit day the mourner leads the services, recites the Kaddish, Bareku and fasts on that day, it is treated as a day of mourning. BaḤ writes that in a leap year (v. supra § 391, 2) the Yahrzeit day is not regarded as a day of mourning since it takes place a month later and is not the concluding day of the twelve month period. however, TaZ a.l.; supra § 391, 3 Gloss end and notes; infra § 402, 12 Gloss. [viz.,] to treat it [in accordance with] the law of the twelve months' [period of mourning] and this is the proper [usage].