Question: If one forgot to count on Thursday night and only remembered after he made early Shabbos. Can he still count Thursday’s Omer since it is still light outside?
The mitzvah is to count the days and weeks from the second day of Pesach until Shavuos. One is required to count sefirah at night.
One who forgets to count sefirah at night may count during the day without a bracha, and then continue counting the rest of the days with a bracha. If one forgets to count sefirah at night and does not remember to count by day, he may not count with a bracha thereafter.
In answering this question some Achronim refer to a similar halacha from the Taz. The Taz (Teshuvos 600) discusses a scenario where a community did not have a shofar on Rosh Hashanah, which fell out on Friday. After the community accepted Shabbos early, a non-Jew brought them a shofar. The question was, do we still consider it daytime and thus the shofar can still be blown, or is it nighttime and there is no longer a mitzvah to blow shofar? The Taz gave two reasons for why they could blow shofar. First, accepting Shabbos is similar to making a neder, whereby if it was done mistakenly it is not valid. Since the community would not have accepted Shabbos if they knew that they would be receiving a shofar afterwards, the acceptance was done mistakenly, and is not valid.
Second, the Taz, quoting the Beis Yosef in the name of the Smag, says that in regard to calculating the eighth day for a bris milah we only look at whether it is actually day or night. It does not matter if one davened Ma’ariv or accepted Shabbos early; if it is still day the bris will be eight days from the day, not from the night. The Vilna Gaon explains that mitzvos that are not dependent on Shabbos – even if one accepts Shabbos early – are considered as if done during the day. Based on this the Taz ruled that they could blow shofar – even after accepting Shabbos.
Rav Moshe Feinstein (Igros Moshe Orach Chaim 4:99:3) discusses whether the Taz’s ruling can be applied to the question of Sefiras Ha’Omer. The first point that the Taz used to permit the community to blow shofar after they accepted Shabbos early was that it was considered that they accepted Shabbos mistakenly, since they would not have accepted Shabbos had they known that a shofar was going to be brought. Rav Moshe says that this reasoning can only apply if one only accepted Shabbos (i.e. said “Mizmor shir l’yom haShabbos), but has not yet davened Ma’ariv. But if one already davened Ma’ariv, we will not consider the acceptance of Shabbos to be mistaken.
This is because there are several variations from the Taz’s scenario. In the Taz’s example, the ruling affected an entire community. When an entire community mistakenly accepts Shabbos early, even if they davened Ma’ariv, they do not repeat Shemoneh Esrei. Regarding Sefiras Ha’Omer, however, we are generally discussing an individual who forgot to count the night before. The halacha is that an individual must repeat the Shemoneh Esrei if he mistakenly accepts Shabbos (see Shulchan Aruch Orach Chaim 263:14). Therefore, if we would consider the individual’s acceptance of Shabbos to have been done mistakenly, it will result in rendering the seven brachos that he davened in Shemoneh Esrei to be berachos levatalah – since he must repeat Shemoneh Esrei. How can we render the acceptance of Shabbos a mistake, in order to fulfill a mitzvah m’d’rabbanan (according to many opinions Sefiras Ha’Omer is only m’d’rabbanan nowadays), if by doing so we create seven brachos levatalah? And perhaps even if it was in order to gain a mitzvah d’Oraisa – if we are discussing an individual’s acceptance of Shabbos where he already davened and will have to repeat Shemoneh Esrei – we would not consider his acceptance of Shabbos to be a mistake, since this would leave him with seven berachos levatalah.
In other words, in order to nullify one’s acceptance of Shabbos we must weigh all of the affects it will have and determine whether it is beneficial for him.
Based on this I thought that it would depend on what day of the omer this occurred. There are seven brachos in the davening on Shabbos. If this scenario occurs after the 7th day of the Omer, the scale is tilted in favor of considering the acceptance of Shabbos a mistake. Since if one does not count sefirah for an entire night and day he has lost the mitzvah, and all of the brachos that he recited until that day are retroactively levatalah, it would be more beneficial for him to nullify his acceptance of Shabbos and remain with fewer brachos levatalah.
Concerning the halacha in this circumstance Rav Moshe rules that (regardless of what day in the Omer it is) even after one has davened Ma’ariv, he may count the sefirah of the previous day – provided that it is still daytime.