Question: What if someone forgot to count sefirah Thursday evening but only realized after he finished davening Friday evening? The catch is that he accepted Shabbos early so that it is still light outside. Can he still count for Thursday evening and then count for Friday night with a berachah once it gets dark?
(As this question is timely, we again interrupt our discussion of “Arabs Circumcise At 13,” which, please G-d, will continue next week.)
It is precisely because of scenarios like the one you describe that some people are reluctant to take in Shabbat early during sefirah. Nevertheless, many do because they have young children whom they wish to include in the Friday night meal but who need to go to sleep at a reasonable hour. Alternatively, they themselves cannot wait to eat when Shabbat starts late since they need time to properly digest their food before they go to bed.
The short answer to your question is that a person may still count the Omer for Thursday evening after Friday night davening if it is still light outside and continue counting that night and subsequent nights with a berachah (HaGaon Rabbi Moshe Feinstein, Responsa Iggrot Moshe, Vol. 6; Orach Chayyim, Part 4, 99:3).
For an explanation, let us examine one of the laws regarding a niddah. The Torah (Leviticus 15:28) states, “Ve’im toharah mizovah vesafra lah shiv’at yamim ve’achar tit’har – If she ceases her flow, she must count for herself seven days and after that she can be purified.” According to the Rema (Yoreh De’ah 196:11), this woman first needs an interval of five full days from the cessation (a bride waits only four days), then she checks, dons “whites,” and begins to count the seven days.
Now, what if the evening that the woman is supposed to don “whites” and begin the count is a Friday night and her congregation accepted Shabbat early? Can she begin her count at shekiah that night after five full days (as these five days must be full 24-hour days), or must she wait until Motza’ei Shabbat?
The Rema (infra Yoreh Deah 196:1) cites two views. The Terumat HaDeshen maintais that she must wait until the following evening to begin her count of seven days. The Agur, though, in the name of the Maharil, maintains that the congregation’s acceptance of Shabbat has no bearing on her and she can start her count that evening. The Rema writes that our custom is to rely on the view of the Terumat HaDeshen. Post facto, however, the view of Agur can be relied upon.
The Taz writes that Sefirat HaOmer serves as a proof for the Agur’s view since we know that even though tosefet Shabbat – adding time to Shabbat – is a biblical concept, we can’t count Friday evening’s sefirah until it is actually dark.
It is obvious that the Taz took a cue from Tosafot (Ketubbot 72a, s.v. “Vesafra lah, le’atzmah”), who ask the following: Why doesn’t a niddah make a berachah on her counting just like we make a berachah when counting the Omer? After all, the Torah stats regarding a niddah, “ve’safra – she shall count,” which is the same language it uses for Sefirat HaOmer.
Tosafot answer that the only proper comparison would be to yovel “since [beit din] can always count correctly, with absolute certainty, similar to Sefirat HaOmer. However, regarding a niddah, it is possible that her count may be overturned [and not be completed]. Therefore she may not count with a blessing.”
We see that the counting of the Omer is comparable to the counting of the niddah, and what applies to one therefore applies to the other (in regards to the counting itself, not the blessing). The actual time for counting in both situations begins at nightfall.