THE MAYAN CIVILIZATION 107 
calendar and nearly as accurate as that of the present 
Gregorian calendar put into service as late as 1582. 
The true length of the year was probably obtained by 
observations of sunrise or sunset on summer or winter 
solstices. From some fixed point of observation, such 
as the doorway of a temple, the extreme point on the 
horizon reached by the sun in its northward or south- 
ward march could be accurately determined. Over a 
period of years the average solstitial period (tropical 
year) could be readily obtained if only the days were 
recorded and the intervals compared. 
Although we ourselves depend mostly upon the year 
count rather than the day count we must remember 
that the annual calendar was only one of several that 
the Mayas brought into relation to the inviolable count 
of days. The lunar and Venus calendars will be con- 
sidered presently. But if the “‘leap year”? days were 
not interpolated, of course, the named months had 
no fixed positions in the year but swung slowly round the 
circle. According to the table of Landa, compiled 
about 1566, the month Pop, which seems to have been 
regarded as the first of the year in ancient as well as 
modern times, began on July 16 O.S. Outside of the 
Mayan area the retrogression of the months is attested 
by actual statements of early Spanish writers. But the 
conventional 365 day year was, after all, sufficiently 
accurate to serve the needs of agriculturists and since 
retrogression was only about one day in four years, 
associations between the months and the seasons would 
hold true for the average lifetime. 
The Lunar Calendar. The revolution of the moon 
around the earth was used by the Mayas in what may be 
called the lunar calendar. It has already been ex- 
plained that an early lunar period of thirty days seems 
