ahn (time) the Gorean hour of which there are 20 in a Gorean day, numbered consecutively. The tenth Ahn is noon and the twentieth is midnight. Each Ahn consists of forty Ehn or minutes, and each Ehn of eighty Ihn or seconds.

The shadows of the pasang stones had grown long, and, judging by the angle of these shadows (for the stones are set in such a way as to serve also as sundials) it was past the fourteenth Gorean Ahn, or hour. The Gorean day is divided into twenty Ahn, which are numbered consecutively. The tenth Ahn is noon, the twentieth, midnight. Each Ahn consists of forty Ehn, or minutes, and each Ehn of eighty Ihn, or seconds. 
Book 2, Outlaw: pg 26
There are twenty hours, or Ahn, in the Gorean day. The hands of the Gorean chronometers do not move as the hand of the clocks of the Earth. They turn in the opposite direction. In that sense, they move counterclockwise. This chronometer, tooled in Ar, was a fine one, sturdy, exact. It contained, too, a sweeping Ihn hand, with which the tiny Ihn could be measured. 
Book 10, Tribesmen: pg 352