An SF novel about monasteries which are isolated from the external world for 1, 10, 100 or 1000 years [duplicate]

Question

I read this SF novel about 10-15 years ago. I think I read it shortly after it was first published.

In this novel there are monks (though the word used is not "monks" but I don't remember exactly what) which are submitted to very strict rules including lots of rituals involving time. There are things to do at special times of the day, of the week (or decade ?), of the month (or sequence of 100 days ?), of the year.

I don't remember much about the book except that the monks can only communicate with the external world once a year, during some Festival. But there are "higher monks" who can only interact with the external world and "lower monks" every ten years. And still higher ones who can only interact with the external world and "lower monks" every hundred years (I suppose "ten year monks" can become "hundred year monks" at least every ten years, otherwise how could "hundred years monasteries" survive ?) and maybe even "thousand year monks" but certainly "thousand years monasteries" must accept new monks more often than every hundred years from "ten years monasteries" and "hundred years monasteries".

I don't remember anything else. Just that IIRC it was written by a rather famous SF author, but I don't remember who.

Answer 1

This is Neal Stephenson's Anathem.

Quoting from the plot summary on Wikipedia:

Anathem is set on the fictional planet of Arbre. Thousands of years before the events in the novel, the planet's intellectuals entered concents (monastic communities) to protect their activities from the collapse of society. The avout (intellectuals separated from Sæcular society) are banned from possessing or operating most advanced technology and are supervised by the Inquisition, which answers to the outside world. The avout are normally allowed to communicate with people outside the walls of the concent only once every year, decade, century, or millennium, depending on the particular vows they have taken.