On the fifteenth day of the seventh month there shall be the Feast of Sukkot to the Lord, seven days. The first day shall be a sacred occasion: you shall not work oat your occupations; seven days you shall bring offerings by fire to the Lord. On the eighth day you shall observe a sacred occasion and bring an offering by fire to the Lord; it is a solemn gathering: you shall not work at your occupations.
– Leviticus 23:33-36
No one is sure when the holiday of Simchat Torah began to be observed. In fact, it is not really a holiday in its own right – which doesn't detract from its popularity. Sukkot, according to the Torah, is a seven day festival. The Torah commands observing an additional holiday for one day that is not actually part of Sukkot (so one is not obligated to dwell in the sukkah or wave the lulav/etrog); this is called Sh'mini Atzeret, "the eighth day of assembly." It has no particular ceremonies other than abstaining from work and bringing certain sacrifices to the Temple. Some say that since Sh'mini Atzeret was sort of an orphan, a holiday all dressed up with nowhere to go, some time in the Middle Ages, the day was connected with the turning point in the cycle of reading the Torah. Some say it originated in Babylonia; others try to prove it started in Israel.
One argument for believing in a Babylonian origin is that it has always been celebrated, throughout the Diaspora, only on the second day of Sh'mini Atzeret, not on the first. From Talmudic times, the festivals (Sukkot, Sh'mini Atzeret, Pesach, and Shavuot) have been celebrated for one day in Israel but for two days in the Diaspora. This originates from the time when the calendar was determined by observation of the new moon; it took time for the news about the determination of the month to travel from the center in Jerusalem to the communities in Babylonia, so to cover all options, Rosh Chodesh was observed for two days, which meant that any date within the month also had a one-day margin of error. Had Simchat Torah originated in Israel, you would expect it to be observed on the first day – and therefore both days in the Diaspora – of Sh'mini Atzeret. However, celebrating it on only the second day supports one popular explanation, that not only was Sh'mini Atzeret an orphan holiday with no colorful customs, but it was two days long – really boring – so the second day was given its own special status as Simchat Torah.
In Israel Sh'mini Atzeret and Simchat Torah are the same single day. Reform Judaism eliminated the custom of second days of holidays in the Diaspora, which means that Simchat Torah had to move up to coincide with the one day of Sh'mini Atzeret, just like in Israel. Thus Simchat Torah is the only holiday that is observed on different days by different parts of the Jewish people.
But wait, there's more: Apparently, in 16th century Safed, a custom began of continuing the celebration of Simchat Torah beyond the day of Sh'mini Atzeret into the evening, after the holiday had officially ended. This led to the modern Israeli custom of hakafot shniyot, "repeat processions:" The night after the holiday has ended, public celebrations are held, with singing and dancing – and since it is no longer holiday, people can travel, and instruments and amplifiers can be used. Thus, Israelis have the opportunity to celebrate Simchat Torah in synch with their fellow [Orthodox and Conservative] Jews in the Diaspora who are only just starting the holiday that evening. Indeed, some say that this modern custom started in Tel Aviv during the Holocaust as a symbol of identification with the Jews of Europe who could not celebrate.
Of course, hakafot shniyot may be public and popular but they are conducted according to Orthodox standards, which leaves half of us out. But this year, in our neighboring town of Karmiel, the Reform and Conservative congregations are uniting to hold their own public egalitarian hakafot shniyot celebration. So Sh'mini Atzeret continues its evolution…Chag Sameach!