Halakhah su Levitico 23:16

A problem does, however, arise with regard to fulfillment of the mizvah of sefirat ha-omer, the counting of the 49 days between Pesaḥ and Shavu'ot. Ostensibly, the counting of the days of the omer does not necessarily entail the counting of consecutive days of the week or of consecutive days of the month, but simply of consecutive twenty-four-hour periods. Thus it might appear that the traveler may ignore the date of the month in the locale in which he finds himself and continue counting consecutive days in seriam. This, however, would lead to an incongruity with regard to the observance of Shavu'ot. The traveler journeying from east to west will find that the festival occurs one day prior to his completion of the counting of seven full weeks; the traveler journeying from west to east will complete the counting of the seven-week period but will experience a delay of one day before Shavu'ot is observed in the area in which he finds himself. Scripture, however, commands that the festival be observed on the day immediately following completion of the counting of the seven-week period: "Until the morrow after the seventh week shall you number fifty days and you shall bring a new meal-offering unto the Lord" (Leviticus 23:16). Thus, the observance of Shavu'ot is inexorably linked to the counting of the omer. Moreover, the counting of the days of this seven-week period is associated with the offering of a sacrifice of the newly harvested produce. The reckoning is essentially the counting off of days until the arrival of the appointed time for the offering. Since the offering is a single communal act it would be somewhat incongruous to define the counting of the omer as a personal, and hence variable, act with the result that a person may complete his own reckoning either a day earlier or a day later than the day associated with the meal-offering.¹⁵A somewhat related question arises with regard to the observance of Chanukkah. Although the eight-day observance commemorates the miracle of the cruze of oil, the kindling of the Chanukkah lights each night during an eight-day period is not a unitary obligation, i.e., an observance which commences on the 25th of Kislev and continues for eight consecutive days without regard to calendrical considerations. Were that the case, the traveler who crosses the halakhic dateline during the week of Chanukkah would continue to kindle the Chanukkah lights for a complement of eight days commencing with the evening of his own first kindling. Since, however, the obligation is not unitary, but rather eight discreet obligations which devolve upon the individual on each of the days of Chanukkah, a voyager crossing the dateline will be bound to the same observance as the indigenous inhabitants of the locale in which he finds himself. Thus, a traveler journeying from east to west will miss one day and kindle Chanukkah candles for a total of only seven days, while a traveler journeying from west to east will observe an additional day and kindle the lights for an aggregate of nine days. Similarly, it would appear to this writer that a traveler journeying west to east on the last day of Chanukkah, or during the evening following the last day of Chanukkah, must also kindle the Chanukkah lights that evening since, subsequent to crossing the dateline, he finds himself in a locale in which the date is that of the last evening of Chanukkah. Cf., however, Rabbi David Schorr, Ha-Pardes, Nisan 5735.
However, with regard to circumcision, which must be performed on the eighth day subsequent to birth, and redemption of the first-born which must be performed on the thirty-first day, it would seem that the days are reckoned in terms of cycles of sunset and sunrise without regard to whether or not the dateline has been crossed. R. Isaac Liebes, Teshuvot Bet Avi, I, no. 111, adopts this view in a responsum concerning redemption of the first-born. It would appear that the same principle would govern determination of halakhic maturity upon attaining the age of thirteen years and one day in the case of a male or twelve years and one day in the case of a female. Cf., however, the discussions of those questions in R. Betzalel Stern, Teshuvot Be-Ẓel he-Ḥokhmah, I, nos. 75-76. For a discussion of the import of crossing the dateline with respect to some aspects of menstrual laws, see R. David Spira, Teshuvot Bnei Ẓion, I, no. 14, sec. 24.

That is that He commanded us to count forty-nine days from the harvesting of the omer. And that is His, may He be exalted, saying, "you shall count for yourselves seven weeks from the morrow of the Shabbat, etc." (Leviticus 23:15). And you should know that just like the court is obligated to count the years of the Jubilee, year by year [and] cycle by cycle - as we explained in what came previously (Sefer Hamitzvot, Positive Commandments 140) - so too is each and every one of us obligated to count the days of the omer, day by day and week by week. And that is His having said, "you must count fifty days" (Leviticus 23:16), and "Seven weeks shall you count for yourself" (Deuteronomy 16:8). And just like the commandment of counting the years and the sabbatical cycles is one commandment - as we explained - so too is the counting of the omer, one commandment. And do not be fooled by their saying (Menachot 66a), "It is a commandment to count days and it is a commandment to count weeks," and think that they are two commandments. For it is a commandment to do each and every part of commandments that have have different parts. However had they said, "From where [do we know that] the days are a commandment; and from where [do we know that] the weeks are a commandment" - it would have been two commandments. And this will not be lost on the one that will not be fooled by the words. Since were you to say, "It is an obligation to do such and such," it surely does not necessarily make that action a separate commandment. And the clear proof for this is our counting every night that it is such and such weeks and such and such days. And were it to be a separate commandment, we would only arrange its content on the night of Shavuot; and we would say two blessings - on the counting of the omer; and on the counting of the weeks of the omer. But the things are not like this. Rather the commandment is counting the omer daily and weekly [together], as they ordained. And women are not obligated in this commandment. (See Parashat Emor; Mishneh Torah, Daily Offerings and Additional Offerings 10.)

The commandment of the sacrifice of the new meal-offering from wheat on the day of [Shavuot]: To sacrifice leavened bread from the new wheat on the day of the festival of Shavuot. And that is what is called in Scripture, "a new offering" (Leviticus 23:15). And they are two loaves, as it is written (Leviticus 23:16), "From your inhabitations you shall bring bread of waving, two of two issaron." And the matter was such that they would bring three seah of new wheat and rub them and pound them in the way of all of the meal-offerings. And they would grind them and sift two issaron in twelve sieves. And they would take them and make two loaves from them and bring leavening (Menachot 52b) and put it into the issaron. And the length of each loaf was three handbreadths and its width was four, and its height was [the span of] four fingers (Menachot 96a). And they were square; and they were baked on the eve of the holiday. And on the morrow after their waving, they were eaten by the priests that whole day and half the night (Menachot 100b). And that meal-offering is the first of all of the meal-offerings [of that crop] of wheat. And with the bread, they would sacrifice seven unblemished sheep, one young bull and two rams for a burnt-offering, a goat for a sin-offering and two lambs for a peace-offering - and these are the sacrifices spoken about in [the Book of Numbers]. All of this was brought with the bread besides the additional offering of the day which was two bulls, one ram and seven lambs for a burnt offering, and one goat for a sin-offering - and these are the sacrifices spoken about in the Book of Leviticus. And it was elucidated explicitly so in the fourth chapter of Menachot 45b that this sacrifice would come with the bread, separate from the additional sacrifice of the day. And after the waving of the bread, it was eaten by the priests with the lambs of the peace-offerings.