– Q. The Rov of our shul mentioned that people should help in determining and publishing the times for davening and shiurim of the shul. He said that there is a very special and great mitzva for someone to write the times and schedule of the tefilos and shiurim of a shul, is that really true?

A. Talmud (Shabbos 75a) mentions that “Rav Zutra said in the name of Rav, that one who knows how to calculate astronomical seasons and the movement of constellations, and does not do so, one may not speak with him because his actions are improper.

Rabbi Shimon ben Pazi said that Rabbi Yehoshua ben Levi said in the name of Bar Kappara: Anyone who knows how to calculate astronomical seasons and the movement of constellations and does not do so, the verse says about him: “They do not take notice of the work of G-d, and they do not see His handiwork” (Isaiah 5:12).

Rabbi Shmuel bar Naḥmani said that Rabbi Yoḥanan said: From where is it derived that there is a mitzva incumbent upon a person to calculate astronomical seasons and the movement of constellations? As it was stated: “And you shall guard and perform, for it is your wisdom and understanding in the eyes of the nations” (Deuteronomy 4:6). What wisdom and understanding is there in the Torah that is in the eyes of the nations, i.e., appreciated and recognized by all? You must say: This is the calculation of astronomical seasons and the movement of constellations, as the calculation of experts is witnessed by all.”

The Smag (Mitzvas Asei 47) deduces from the above that it is also a mitzva to know when exactly our Yomim Tovim will be as is done when making and publishing a luach. (See Peninei Halacha – Shabbos 75a).

Rabbi A. Bartfeld as revised by Horav Yaakov Hirschman, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a.