Arab Tridua: Three-Day “Weeks” in Arabia

This post is about a rather neglected aspect of time division in early Arabia. In his Fawā’id (IV, 7) Ibn Mājid explains: “Every month is divided in ten parts of three days each, and each part has its name.” Then he lists the ten triads or, more specifically, tridua: Ghurar, Nufal, Tusa‘, ‘Ushar, Buhr, Bīd, Durā‘, Muhāq, Hanādis, Ziyād, Surar. Most of the names are straightforward in meaning, relating to the appearance of the moon or to the date count, and the word “three” is implicit. For example, “The three of Tusa‘” (al-thalāth al-tusa‘) means something like “the three [days] of the ninth”, because this triad ends on the ninth day of the lunar month. Al-thalāth al-bīd means “the three of whiteness”, because they are near the full moon.

Keen-eyed readers will have noticed that the above list actually contains eleven tridua, not just ten. This means to reflect the garbled textual condition in which Ibn Mājid’s list reached his readers in the 15th century, with obvious ingrained misspellings and interpolations. The earlier references I can find for these names are Ibn Wādih al-Ya‘qūbī (9th century) and al-Bīrūnī (11th century), who give slightly different lists. In comparison to them, Ibn Mājid’s does look like the outcome of centuries of Chinese whispers.

Now, al-Bīrūnī explains first that the names are derived “from the distinctness revealed by the state and the curvature of the moon,” and shortly after that they are “taken from the faces of the moon and its curvature.” This is what I find warrants a thought on our concept of “week”. Our weeks derive in part from a division of the lunar cycle in quarters.

Let us leave aside for now the numerological relevance of the division in three, seven or ten, which we have discussed previously. We can see how the beautiful continuum of the lunation allows for as many divisions as our powers of observation allow us to determine distinct—hence nameable—units. How many nights do we need to appreciate each clearly distinct aspect of the moon?

Nama-rupa, in the Sanskrit philosophical terminology, “name-form”: mutually dependent and inseparable aspects of every phenomenon, everything that appears to then vanish “under the Sun.” The gentle and ever-so-fleeting light of the moon is perhaps the phenomenon par excellence, now there, now vanished… What is left to us, puny sublunary creatures is to wield our power to name, and thus, by naming, to create scientia, the knowability and the knowledge, a “possession for ever.” [JA]