http://www.olwydd.org/misc/time.php

Error: "Four days make up an andu (an andu is therefore equal to an Earth day). There are ten andaen, named for certain of the Immortals."

Twelve anlaen (half hour segments) make up an andu (6 RL hours, one IG day), and four andaen make up a week. A week is a real life day. There are ten weeks, which is 40 andaen, in a month.

TIME HELP is a little odd in its description:

>>An Elanthian Day is called an "ANDU." Each andu is divided into twelve parts, called "ANLASAEN" or more commonly "ANLAEN" (the singular for both is ANLAS). An anlas is roughly a half hour of real life time. In turn, each Anlas is divided into minute-long units called "ROISAEN" (the singular is ROISAN). Now, in High Gamgweth, "ANDU" actually means "day," but since each real life day here is really four days long for our characters, "weeks" is the common translation.

However, the only confusing part is the last sentence seeming to be a contradiction in its wording. The first sentence verifies that an andu is twelve anlaen long, and there are obviously 48 anlaen in a week, thus an andu must be a day with 4 andaen in a week, aka RL day.