May I Establish a Personal Yom Tov?
The question of whether one may commemorate a miracle that happened to them or to their Rebbe by establishing a personal Yom Tov, is discussed by poskim who address the following issues:
The Gemara discusses a work called Megilas Taanis, which documents all of the dates of positive events that took place throughout the era of the second Beis Hamikdash, and the varying levels of simcha that had been assigned to them. The Gemara states that “Batlah megilas taanis,” (this work is no longer binding), and that being the case, “Havu d’lo losif alah,” (there certainly is no room for adding more such days to the calendar). This would appear to negate the idea under discussion here. However, poskim explain that the Gemara refers exclusively to events that occurred during the Bayis Sheini period, not those that took place later; therefore, it does not preclude establishing a Yom Tov to commemorate a personal miracle.
There is a prohibition of bal tosif (not to add to what the Torah explicitly states), which suggests that adding Yomim Tovim to those cited in the Torah would not be allowed. However, poskim explain that it’s certainly permissible to mark a day when one was saved mi’maves l’chaim (one’s life was spared), and that the Torah itself expects people to express their gratitude to Hashem by celebrating.
In any case, this question is moot as long as the date isn’t marked as a regular Yom Tov—when work is forbidden and other applicable halachos are observed—and especially if it isn’t framed as something obligatory, but rather as one’s personal custom. In practice, throughout history numerous Jewish communities have established local holidays, or “Purims”, to mark miraculous events that transpired to them or their leaders. #455
אא״פ להאריך במסגרת זו בכל הפרטים. ובאו רק ציונים אחדים לכללות הענין - שו״ת מהר״ם אלשקר סמ״ט - הו״ד במג״א סתרפ״ו סק״ה. וכן מצינו שקבע בעל התויו״ט לצאצאיו אחריו, וכמפורט בס׳ מגילת איבה. (וראה שו״ת שבה״ל ח״י סק״נ). והוא דלא כדעת הפר״ח או״ח סתצ״ו סקי״ד. וראה מש״כ ליישב בשו״ת חת״ס סקצ״א. ועיי״ש סקס״ג. סר״ח. יו״ד סרל״ג. וראה חיי״א כלל קנה סמ״א. ועייע בשד״ח מערכת יו״ד כלל נג. וכבר העירו ממאירי שבת יג, ב. וי״ל.
ולענין בל תוסיף - ראה רמב״ן ואתחנן ד, ב. פנים יפות שם. מנ״ח מ׳ תנד. וראה טל תורה מגילה יג, א. כלי חמדה פורים סל״ה. והאריכו בזה בכ״מ, ובפרט - בדור האחרון. ואכ״מ. וד״ל.
וראה כה״ח סרי״ח סק״ט - לענין אי אמירת תחנון.