In a second attempt to translate the Torah into Greek (after an unsuccessful attempt 61 years earlier), the ruling Greek-Egyptian emperor Ptolemy gathered 72 Torah sages, had them sequestered in 72 separate rooms, and ordered them to each produce a translation. On the 8th of Tevet of the year 3515 from creation (246 BCE) they produced 72 corresponding translations, including identical changes in 13 places (where they each felt that a literal translation would constitute a corruption of the Torah's true meaning). This Greek rendition became known as the Septuagint, "of the seventy" (though later versions that carry this name are not believed to be true to the originals). Greek became a significant second language among Jews as a result of this translation. During Talmudic times, Tevet 8 was observed by some as a fast day, expressing the fear of the detrimental effect of the translation.

Links: The Day Before; Translating Truth; more on translation