“On the round clock beside it, the numbers lay in an indecipherable heap, as if they’d come unglued. Just above them were printed the words WHO CARES?
This was what we found ourselves saying whenever anyone asked the time.
In other words, the time between Pesach and Shavuot is not the timeframe within one may fulfill this mitzva. Rather, these are the days that one must count in order to fulfill the mitzva. The time does not obligate or generate the mitzva, but rather, it is the mitzva itself!
if a mitzva can theoretically be performed any time, but other factors determine that it can only be performed on certain days, it is not considered to be a time-bound mitzva. Therefore, sefirat ha-omer, which is dependent not upon specific days, but rather upon the bringing of the korban ha-omer on Pesach and the shetei ha-lechem on Shavuot, is not considered a time-bound mitzva (see Turei Even, Megilla 20b).
The Ramban (Kiddushin 33b), however, enumerates mitzvot that are not time bound and which women are therefore obligated to perform. He includes respecting and honoring parents, bikkurim, challa, kisui ha-dam, reishit ha-gez, matanot kehuna, perika u-te’ina, and pidyon peter chamor - as he summarizes, “most of the mitzvot.” The mitzva of sefirat ha-omer is included in this short list of examples of mitzvot that are not time-bound. R. Malkiel Zvi b. R. Yonah Tannenbaum (1847-1910), in his Divrei Malkiel (3:5), as well as R. Soloveitchik (Nefesh Ha-Rav p. 191), were apparently so shocked by this opinion that they suggested that this must be a scribal error!
The Talmud (Kiddushin 33b) rules in numerous places that women are exempt from “time-bound commandments,” “mitzvot asei she-ha-zeman graman.” Women are therefore exempt from certain mitzvot, such as tefillin, tzizit, sukka, arba minim, shofar, and keri’at shema. Seemingly, sefirat ha-omer, which is performed between Pesach and Shavuot (and preferably at night), should be considered such a mitzva.
The Abudraham explains that the farmer, who spends the time after Pesach occupied with the wheat harvest, may lose track of time and forget to come to Jerusalem for the celebration of Shavuot. Therefore, he is commanded to count forty-nine days, after which he celebrates Shavuot in Jerusalem. Rabbeinu Yerucham (Toldat Adam Va-Chava, netiv 5, part 4) explains the mitzva in this manner as well, and he therefore suggests that one counts at night because one is less burdened by the harvest at night.
The reason for which the Holy One, blessed be He, commanded to count the omer was because each Israelite was involved in his own harvest and each one was dispersed in his own threshing floor, and He commanded to count in order that they should not forget the time of their ascent for the festival (aliyah la-regel).
As the tally shows about a man that all of his deliverance and all of his desire is to reach that time. And that which we count to the omer, meaning, "Such and such days have passed from the tally," and we do not tally "Such and such days do we have to the time," is because all of this shows us the great desire to reach the time [of Shavuot].