The last of the Elders (z'keinim) who were contemporaries of Joshua and outlived him, passed away in the year 2533 after creation. They were part of the chain of Torah transmission as listed at the beginning of Ethics of the Fathers: "Moses received the Torah from Sinai and gave it over to Joshua. Joshua gave it over to the Elders, the Elders to the Prophets..."
In ancient times, this day was marked as a fast day.
[Some are of the opinion that this occurred on the 5th of Shevat].
Chabad-Lubavitch Chassidim observe the special customs of the Shabbat
prior to the yahrtzeit (anniversary of the passing) of the sixth
Lubavitcher Rebbe, Rabbi Yosef Yitzchak Schneersohn (1880-1950), which
occurs next week, on the 10th of
Link:A Letter from the
Lubavitcher Rebbe outlining his suggested observances for the Shabbat
preceding Rabbi Yosef Yitzchak's yahrtzeit.