Back in the eighth and ninth century CE, in the region of Persia, there were many who balked at the notion of oral Torah. They seemed to feel that all we need is what is written, what was given by the Almighty, without the Oral Law. These folks banded together in sects, loosely known as Karaites, which literally means “people of the Scripture,” as in likro (לקרוא), to read. Ultimately the movement spread to Egypt and Syria and even to Spain and Turkey, becoming distinct in ideology and practice from those who kept with the oral tradition, the Rabbanites or Rabbinical Judaism (which is what most Jews identify with today).
Not only do the Karaites deem the Talmud to be of human origin and therefore not holy enough for reverence, they also believe in literal interpretations. They have permitted personal interpretation, as well, which is the derivation of their name. For instance, without the rabbinic interpretation that a light may be kept burning from before the Sabbath, a Karaite may opt for darkness on the Sabbath, based on Exodus 35:3, “You shall kindle no fire throughout your settlements on the Sabbath day.”
Eventually, the Karaites seem to have made their own oral tradition, especially as they adopted stricter rules. Asceticism seems to have taken hold and emphasis was placed on things that made life more rigorous. For instance, some felt that it was also forbidden to heat oneself on a cold Shabbat. Similarly, marital relations would be curtailed on Shabbat. Hanukkah was downplayed, tefillin eschewed, and mezuzot abandoned.
One of their earlier scholars, Anan ben David (715-795 CE), was the namesake for their initial designation, Ananites. (Some say that the movement dates back to the Second Temple, but the evidence is sketchy.) By the tenth century, Sa’adia ben Joseph was speaking out against including Karaists as Jews, and this conflict really served to inspire clearer definition of each movement. Scholars and advocates produced a great amount of written work on both Rabbanite and Karaite Judaism, in Hebrew and Aramaic, and much of which is extant today resides at the St. Petersburg Public Library in Russia, which contains a large number of historic Jewish works.
There are approximately 30,000 Karaites living today in Israel, mostly near Ashdod and Ramla, with some in the Crimea as well. (Of course, with their literal interpretation of parts of Genesis 32, they resist counting themselves.) And what about Shavuot on Sunday? They interpret the counting of the omer to begin on the Shabbat after Pesah, and thus Shavuot would always occur on a Sunday.