The basic structure of the Mayan calendar is common to all calendars of (i.e., the civilized part of.... dai name

It consists of a ritual cycle of 260 named days and a year of 365 days. These cycles, running concurrently, form a longer cycle of 18,980 days, or 52 years of 365 days, called a , at the end of which a designated day recurs in the same position in the year. The names of the days differ in the languages of Mesoamerica, but there is enough correspondence of meaning to permit the correlation of the known series, and there is reason to think that all day cycles were synchronous. The 365-day year was divided into 18 named months of 20 days each, with an additional five days of evil omen, named Uayeb. Since both the year and the number (20) of names of days are divisible by five, only four names combined with 13 numbers could begin the year. To identify a date of the Calendar Round, they designated the day by its numeral and name, and added the name of the current month, indicating the number of its days that had elapsed by prefixing one of the numerals from 0 through 19. To corr! elate all historical records and to anchor dates firmly in time, the Maya established the , a continuous count of time from a base date, 4 Ahau 8 Cumku, which completed a round of 13 baktuns far in the past. It shows that the Calendar Round date that follows falls 1,243,615 days (just under 3,405 years) after the 4 Ahau 8 Cumku on which the Long Count is based. From this date, distance numbers, called Secondary Series (SS), lead back or forward to other dates in the record, which frequently ends with a Period-Ending (PE) date. This is a statement that a given date completes a whole number of tuns or katuns in the next higher period of the Long Count. Period-Ending dates gradually took the place of Initial Series, and, in northern , where Mayan sites of the latest period are located, a new method of notation dispensed with distance numbers altogether by noting after a Calendar Round date the number of the current tun in a Long Count katun named by its last day. Long Count k! atuns end with the name Ahau (Lord), combined with one of 13 n! umerals; and their names form a Katun Round of 13 katuns . The discontinuance of Initial-Series notations some centuries before the conquest of Mexico by Spain makes all attempted correlations of the Mayan count with the Christian calendar somewhat uncertain, for such correlations are all based on the assumption that the Katun Round of early colonial times was continuous with the ancient Long Count. Glyphs E and D have numerical coefficients that give the age of the current Moon within an error of two or three days; Glyph C places it in a lunar half year; and Glyph A shows whether it is made up of 29 or 30 days. It has been suggested that certain other dates, called determinants, indicate with a remarkable degree of accuracy how far the 365-day year had diverged from the solar year since the beginning of the Long Count, but this hypothesis is questioned by some scholars. dai name