"On the west side of a court at Uaxactun, facing due east, was a pyramid. On the opposite side, on a terrace, were three temples with façades running north and south, and arranged so as to establish lines of sight when observed from the stairway of the pyramid on the west side. From this observation point, the sun, on its way north, rose directly behind the middle temple (Str. E-II) on March 21, the vernal equinox; behind the northernmost front corner of the north temple (Str. E-I, left) on June 21, the summer solstice; behind the middle temple again on its way back south on September 23, the autumnal equinox; and behind the southernmost front corner of the south temple (Str. E-III, right) on December 21, the winter solstice. This assemblage of buildings thus marked the longest and shortest days of the year, as well as the two intermediate positions, when day and night are of equal length."
Robert Sharer, The Ancient Maya, p. 181