I'm going to start with my conclusion. This is my opinion and nothing more. The subject may seem trivial to people for whom it is not relevant, but to those for whom it is, it should matter. In my experience, though, people will make their decision based on convenience.
--Update: someone sent in a mareh makom, a teshuva from Rav Mordechai Breisch of Switzerland. He comes to the opposite conclusion. I recommend that you read this post, and then read his teshuva, and then decide which is more convincing. Specifically, please read paragraph numbered Gimmel on this page and then decide.
--Final Update:
The מהר"י וייל was right.
פסקי הבעלי בתים ופסקי הלומדים הם שני הפכים
~~~~
Kaddish on this Post
and
Post Mortem
Harav Yehuda Oppenheimer sent me a mareh makom to the Biur Halacha in 132. It is clear in the Biur Halacha that Kabbalas Shabbos makes it Shabbos regarding the Yohrtzeit. I could say that "Lomdus is Lomdus, and Halacha is Halacha," but the Chafetz Chaim's בודאי makes it just embarrassing. I'm wrong.
The words of the Chafetz Chaim:
וקדיש של מזמור שיר ליום השבת אם חל היא"צ שלו ביום ו' בודאי אין לו חלק בהם ואם חל היא"צ בשבת משמע מא"ר דשייך להיא"צ
(I don't know why the second half of the sentence doesn't automatically follow the first and why he would need a raya from the Eliah Rabba.)
The Machatzis HaShekel, also pointed out by Harav Oppenheimer, says something amazing and incomprehensible to me. Regarding the Magen Avraham that says
וקדיש שאומרים בערב שבת אחר מזמור שיר ליום השבת הוא לאבלים, אם לא שהיארצייט הוא בחברה של קבלת שבת, והכל לפי המנהג
he says
ר"ל, שיש לו יארצייט בשבת, משא"כ אם היה לו יארצייט בערב שבת אין לו שייכות לקדיש של מזמור שיר ליום השבת שהוא שייך לשבת, אף לדידן דאמירת מזמור לא הוי קבלה עד אמירת ברכו (כמ"ש מג"א סוף סי' רסא) מ"מ אמירת המזמור שיר שייך לשבת דווקא, אחר זה ראיתי שכן כתב גם בתשובת כנסת יחזקאל
which means, in plain English, that it doesn't matter if the person was mekabel Shabbos or not. The Shabbesdikkeh davening belongs to the person that has yortzeit on Shabbos. A Friday yortzeit has no rights to the Mizmor Shir Kaddish, even if nobody is mekabel Shabbos with Mizmor Shir (because they wait for Borchu,) because it is a davening that is related to Shabbos. Even if nobody is mekabel Shabbos at that point, even though it is said before Shabbos. I have no idea how that makes sense. It reminds me of the sign "Kosher style" on some delis. I give up.
Even though Rabbi Oppenheimer has blasted a hole in my boat, here's what I wrote. I still think it's a strong svara. I'd love to argue my mehalach with everyone that says I'm wrong. It hurts to say so, but I have enough seichel to know when I'm beaten.
I've given it some thought, and the post is followed by a which explains where I went off the track, what my derech was and how the poskim understood it differently. We'll call that addendum the POST MORTEM.
Below is the original Post.
The minhag/chiyuv/mitzva of Kaddish on a Yohrtzeit has nothing to do with your Kabbalas Shabbos or Yomtov. If the Yohrtzeit is on Friday, and you make an early Shabbos, you should still say Kaddish at Maariv if the sun hasn't set. If the Yohrtzeit is on Shabbos, and you make an early Shabbos, you are not a chiyuv to say Kaddish at Maariv.
The Maharam in Smachos 117 says that a person that made an early Shabbos and hears a Shmu'ah Krova, his first day of Aveilus is Satuday, even though it's Friday and the Sun is still shining. Early Shabbos makes it Saturday.
The Maharil (Tshuvos 95) says even the Maharam would agree that a woman that made an early Shabbos and made a hefsek tahara after Maariv can count Friday the day of hefsek tahara and begin counting day one on Shabbos. Even if aveilus depends on your kabbalas Shabbos, Niddah does not. Niddah depends on the metziyus of day/night, what he calls "עיצומו של יום", and your kabbalas Shabbos does not change עיצומו של יום.
The Trumas Hadeshen (248) disagrees with the Maharil. He says that after kabbalas Shabbos, it is not Friday any more for hefsek tahara. He doesn't like the Maharil's idea of early kabbala not being able to change our definition of the יום, whether you call it עיצומו or otherwise. He says if that were true, what happened to davening three times a day, where the passuk says ערב ובוקר וצהרים אשיחה ואהמה. If you need to daven ערב ובוקר וצהרים, then who cares that you made an early Shabbos? So you see, he says, that making early Shabbos makes it Erev, it makes it עיצומה של לילה.
The Rema in YD 196 brings the two opinions regarding hefsek tahara, and says that the halacha is really like the Maharil, and it's still Friday for this purpose.
The Mechaber in 402, regarding Aveilus, paskens like the Maharam, that early kabbala makes it Shabbos.
The Shach there says that this is not inconsistent with the Rema that it's Friday for Niddah for hefsek tahara, because the Maharil's distinction is correct. For Aveilus, it's Shabbos. For Niddah, which is talui on עיצומו של יום, it's Friday.
The Trumas Hadeshen there (248) talks about Milah. The child was born Friday afternoon after everyone was mekabel Shabbos. He says that for Milah, everyone will agree that you look at the fact of day/night, irrespective of kabbalas Shabbos. Why? Because the date of Milah is independent of your choices and your status. It is an event that occurs in its own context.- נולד ובא מן השמים ואין בידי אדם לשנותו
דלענין מילה הספק נולד ובא מן השמים ואין בידי אדם לשנותו ואין שייך לומר כאן "הואיל ועשהו לילה שוב אין לעשותו יום דתרי קולי לא עבדינן," דאין אנו עושין אותו יום אלא מן השמים נולד משא"כ לגבי גט ואבילות והפסק בטהרה דכולו בידי אדם הן ימתינו עד למחר ליתן הגט או תפסיק למחר או יקדימו קודם תפילת ערבית והמגיד שמועות האבילות ג"כ בידו היה להקדים או לאחר
So, what about Yohrtzeit? The answer is clear, and underscored by the Trumas Hadeshen. Who cares that you made an early Shabbos? The Yahrtzeit depends on the date of death of the other person, an event external to your decisions and to your status. The yahrtzeit is that day, and it does not matter what you call it.
Aveilus and Shmuah Krova are dinim in the Aveil. The Yortzeit is a din in the meis.
Yamim Tovim have a kedusha that commemorates or re-enacts an event, and individuals have the ability to invoke that kedusha in the afternoon before the calendar date begins. A Yartzeit is purely the reality of an anniversary, and that anniversary begins when it begins. It is both עיצומו של יום and בא מן השמים ואין בידי אדם לשנותו.
True, there might be different aspects of a yahrtzeit, as indicated by the ideas expressed among poskim and Baalei Machshava, namely, the importance of aliyas haneshama on the anniversary of his death and the idea that it is a day of judgment and bad mazal to the child of the niftar. But I think we can all agree that at least in discussing the anniversary of a death, we should not solipsistically decide that the chasan haneshef is the mourner.
No, it does not matter if the niftar was makbael Shabbos early either. I'm not even going to address that.
For further support, please see the Netziv in Sheiltos Vayakhel 67:13. Erev is one thing. Laylah is another. I believe that is another way of saying the Maharil's chiluk, but that it adds support to my reasoning.
אלא נראה דהא מוכח דמצות ערבית שלא כתיב לילה בפי׳ מתחיל הזמן מפלה"מ כמו ק"ש ותפלה ש"ע ואפי׳ החולקים על ר"ת אינו אלא משום דבעינן זמן שכיבה הא בל"ז מודי כ"ע תדע דהתו' ריש פ' ע״פ כ' דמצה ומרור זמנה משתחשך דוקא משום דאיתקוש לאכילת פסח דכתיב ואכלו את הבשר בלילם הזה הא בל"ז כשר מפלה"מ אע"ג דכתיב בערב תאכלו מצות אבל לילה דכתיב בקרא ודאי משתחשך משמע וכן מצוה יומית כמו טבילת נדה דבעינן בשמיני ולא בשביעי ועד צה"כ עדיין שביעי הוא אבל מצוה התלויה בערב ולא כתיב לילה מתחילה המצוה מזמן פלה"מ
I am familiar with the Taz and Maharshal in OC 668. I first heard about them from Reb Chaim Zimmerman when I was around nine or ten years old, in 1961, maybe earlier. He said "Der Taz halt az men ken mechallel Shabbos zein!!" And I've heard them discussed at least five times by people that have to speak between Mincha and Maariv on Sukkos. "The Taz in tof reish samach ches.....................," like Bar Mitzva boys saying "The Gemara in Menachos lamed vov says............." The Taz and Maharshal are not relevant to this discussion.
POST MORTEM
I realized why my approach is so diametrically contradicted by the Machatzis Hashekel and Knesses Yechezkel. I understood the Yortzeit as a day of Kapara and Aliyah for the niftar, as the Zohar and Ari zal say, and therefore akin to the day of Milah, an event that occurs outside human involvement on עיצומו של יום. They obviously hold that the concept of yortzeit is that the day is a day of remembrance for the person, or the day is dedicated to the person. If so, it's a din in the day. If that day is Shabbos, the tefillos of Shabbos are misyacheis to him, even to the extent that a tefilla that is said because it is EREV SHABBOS is misyacheis to that day and therefore to the person whose day it is. In this sense, it is similar to a Yomtov, which remembers an event, but is a din in that day.
Once again, this underlines the Mahari Vayl's famous dictum (brought in the Sma in 3:sk13) that
ואם תשמע לעצתי לא תשב אצל הקהל בשום דין, דידעת שפסקי הבעלי בתים ופסקי הלומדים הם שני הפכים.
I'm not saying this as false humility, so that someone will write in and say "Oh, no, you are a talmid chacham, not stam a baalabos!" My point is that I find that I become very nogei'ah to svaros that appeal to me early in the process, and my mind is no longer as easily opened by seeing a pshat that says different. It's a loss of mental flexibility caused by years of knowing what I know and not seeking new vistas.
Since I mention the Sma, here's a great story about Reb Meir Simcha and the Rogotchover. I wish I could tell it to my father.
מספרים כי פעם נתווכחו ביניהם שני גדולי העולם, הגאון הראגטשובי והאור שמח. בלהט הויכוח ובאין מוצא, הציע הראגטשובי לצאת לרחובה של עיר ולשאול את ההלך הראשון הנקרה בדרכם מהי דעתו. 'הן דעת בעלי בתים היא היפך מדעת תורה... כל אשר ההוא יאמר, נדע שהצדק עם שכנגדו' טען.
קיבל האור שמח את הצעתו ויצאו שניהם יחדיו. היהודי הראשון שבא לקראתם נקרא לבוא אליהם, ושני הגאונים הציעו לפניו את דבריהם. הלה אימץ מעט את מוחו ואמר שנראים לו דברי הראגטשובי.
פניו של האור שמח אורו. 'הנה' קרא 'הרי שצדקו דברי'.
'לא ולא' השיבו הראגטשובי 'הן ערב שבת היום. ואמרו חז"ל שהרץ בערב שבת והזיק - פטור, מפני שרץ ברשות. הרי שבערב שבת דעת האנשים אינה מיושבת ונוהגים הם בפיזור הדעת. אם כן מחמת כן כוון האיש אל האמת, אינו מיושב כעת בדעתו...'
For the sake of family members that read this, I want to explain how the question arose. Friday, July 14, 2017, was the twentieth of Tammuz. I was talking to HaRav Shimon Kalman Goldstein about the anniversary of the murder of the Telzers, and I mentioned that my uncles, my namesakes, Eliezer Yechiel and Nachum Velvel, were among them. A moment before, we had been talking about people that demand the amud to say Kaddish for their aunts and grandparents. I realized that nobody on Earth would ever say Kaddish for my namesakes if I didn't. I, of course, have no chiyuv, but it's the least I can do for my namesakes. So I decided to begin commemorating their yarhtzeit. I made an early Shabbos that afternoon, and during Kabbolas Shabbos I went through the above in my head, and so even though Friday was the twentieth of Tammuz, I continued saying Kaddish after Kabbolas Shabbos.