Yom Kippur

Blow the trumpet in Zion,
declare a holy fast,
call a sacred assembly...
Joel 2:15

From the Yiddish play, The Dybbuk;

God's world is great and holy. The holiest land in the world is the land of Israel. In the land of Israel, the holiest city is Jerusalem. In Jerusalem, the holiest place is the temple, and in the Temple, the holiest spot was the Holy of Holies...

There are seventy peoples in the world. The holiest among these is the people of Israel. The holiest of the people of Israel is the tribe of Levi. In the tribe of Levi, the holiest are the priests. Among the priests, the holiest was the High Priest...

There are 354 days in the [lunar] year. Among these, the holidays are holy. Higher than these is the holiness of the Sabbath. Among Sabbaths, the holiest is the Day of Atonement, the Sabbath of Sabbaths...

There are seventy languages in the world. The holiest is Hebrew. Holier than all else in this language is the holy Torah, and in the Torah, the holiest part is the Ten Commandments. In the Ten Commandments, the holiest of all words is the name of God...

And once during the year, at a certain hour, these four supreme sanctities of the world were joined with one another. That was on the Day of Atonement, when the High Priest would enter the Holy of Holies, and there utter the name of God. And because this hour was beyond measure holy and awesome, it was the time of the utmost peril, not only for the High Priest but for the whole of Israel. For if in this hour there had, God forbid, entered the mind of the High Priest a false or sinful thought, the entire world would have been destroyed.

(From Jewish Literacy by Rabbi Joseph Telushkin)

You'd think that it would just be common courtesy for them to inform - I don't know - the rest of civilization when they did this every year, just in case the world was destroyed one time.
Kind of reminds me of a few months ago when they finally fired up that Supercollider without really telling everyone it might result in a black hole that would basically destroy the fabric of our universe. Just a heads-up might have been nice.

Anyway, Baruch Ha-Shem!