Audio guide:
The reading order of the obverse is from left to right. The first section, which covers the first eight plates of the codex, is an extended ritual calendar called tonalpohualli, or “count of destinies”. The strip of eight plates is divided, in its central part, into five rows of 52 square cells. Each cell records one day so that the entire almanac covers a period of 260 (52 x 5) days, the length of the ritual "year".
Each cell contains two images: on the right is the glyph of one of the twenty-day names, while on the left is the image of one of the nine gods known as the “Night Lords”. Each cell corresponds to an implied number of a repeating sequence from 1 to 13, so each row contains 5 trecenas or periods of 13 days.
The reading begins with the first cell at the bottom left, continues all over the eight plates, and then goes back to the first plate, starting again with the second row from the bottom. In this way, the calendrical sequence ends with the upper right cell of plate 8, which is the 260th day of the count.
The top and bottom rows, composed of rectangular cells, contain various mantic images used by the diviner to add further meaning to each day. The tonalpohualli almanac was used to interpret the value of each day (positive, negative, etc.), which would have influenced any activity performed during that day. The date of a person's birthday, for example, would have determined his or her future destiny.