It is late afternoon on the fifth day of the “third month.” The Israelites are “encamped at the mountain of God” (see Exodus 18:5). In the morning, God will “appear” before all of them collectively and each of them individually.

As night falls, they go to sleep. Hours pass. Suddenly, earth-shattering thunder startles them to frightened wakefulness. There are terrible bursts of lightning upon the mountain, making it appear as if it is aflame, “and all the peopleâ€¦trembled” (verse 19:17ff).

It is quite a dramatic scene, but to the kabbalists of the Middle Ages, there is a problem here. Going to sleep that night was no way to prepare for the encounter of encounters.

And so, somewhere between the 13th century, when its echoes are said to be found within rabbinic texts, and the 16th century, when the kabbalists of Tz’fat made it a standard practice of theirs, the custom of spending the first night of Shavuot studying Torah began. They called it “tikkun leil Shavuot”: the night to “tikkun” or “repair” the wrong-headedness of the Israelites by staying awake all night in anticipation of that fateful moment of Revelation (which, in fact, is re-enacted in the morning with the reading of Exodus 19 and 20).

Many synagogues in our area held Tikkun Leil Shavuot programs this week. The only question is whether they held these programs on the correct night. In other words, was Shavuot really Shavuot?

Yes, it was, but that such a question even can be asked speaks volumes about the ambiguities that turned what arguably is the most important festival on our calendar – our birthday as a holy nation – into the least observed festival.

The Torah does not give us a date for Shavuot. Pesach, the Torah tells us several times, begins in the waning moments of the 14th day of the first month, and “Chag Hamatzot” (“the festival of unleavened bread”) begins moments later as 15th of the month begins. We have an observance on the “first day of the seventh month” – we call it Rosh Hashanah, or New Year’s, even though it falls out in the middle of the year. On the “10th day of the seventh month” we have Yom Kippur. Then, on the “15th day of the seventh month” comes Sukkot, followed the next week by “the Eight Day of Assembly,” or Shemini Atzeret.

Shavuot alone is dateless, and that is just the start of the problem.

Says Leviticus 23:15-16, “And from the day on which you bring the sheaf of elevation offering -the day after Shabbat – you shall count off seven weeks. They must be complete: you must count until the day after the seventh week – 50 daysâ€¦.”

Exactly when we bring this “sheaf of elevation offering” and what “the day after Shabbat” means go unexplained.

The problem is compounded by two verses we just read in shul on Thursday, Deuteronomy 16:9-10: “â€¦start to count the seven weeks when the sickle is first put to the standing grain. Then you shall observe the Festival of Shavuotâ€¦.”

Is “when the sickle is first put to the standing grain” the same as “the day on which you bring the sheaf of elevation offering,” and does that occur on “the day after Shabbat,” whatever that means?

Your guess is as good as anyone’s.

We take “Shabbat” to mean what the sages of blessed memory believed it to mean: the first day of “Pesach” (technically speaking, Chag Hamatzot), meaning that we begin the seven weeks of counting on the second day of that festival. The Torah, in fact, seems to support this reading when it refers to festivals as “shabbatot.”

Not everyone agreed with this, however. The priests of the Second Temple period took “Shabbat” literally and began their count on the first Sunday after Pesach began. Using this counting scheme, this year Shavuot would fall out this Sunday, June 8.

The Qumran community used a fixed solar calendar. Because “Shabbat” to that community meant the first Shabbat after Pesach, Shavuot would fall on the 15th day of a solar Sivan.

Although Ethiopia’s Beta Israel community also took “Shabbat” to refer to Pesach, it interpreted that to mean all of the festival, and so began to count on the day after Pesach ended, making Sivan 12 the date for (June 10 this year). Their Shavuot, however, does not celebrate the giving of the Torah. That festival is Sigd, which falls each year on Cheshvan 29. (It is now a recognized national holiday in Israel.)

This also is due to a built-in ambiguity. The Torah refers to Shavuot as “the Harvest Festival” (see Exodus 23:16), “the Feast of Weeks” (see Exodus 34:22 and Deuteronomy 16:10) and “the Day of the First-fruits” (see Numbers 28:26), but never as “the festival of the giving of our Torah.” In fact, no one seems to have referred to it by that name before well into the second century C.E., most likely because no one associated Shavuot with the giving of the Torah until then.

They debated when Shavuot fell. They debated why it was celebrated. And, absent a Temple, no ritual attaches to it. Is it any wonder so many Jews this week ignored it?

Rather than a Tikkun Leil Shavuot, we desperately need a Tikkun Shavuot period.