Copan, Honduras: Stela 10 and Temple 22.
When looking through the window of Temple 22 toward the western horizon at Copan, Honduras, in the Spring, the sun sets behind Stela 10 sixteen days after Vernal Equinox at an orientation of 276*45'00". Four days later, the sun reaches the mid-line of the window at an orientation of 278*25'00. This second day always falls 20 days after Vernal Equinox and 20 days before solar zenith passage, when the sun is directly overhead at noon, and so precisely, in fact, that vertical objects do not cast a visible shadow at that time. This same sequence, but in reverse order, also occurs in the Fall, when the sun returns to these same orientations relative to solar zenith passage and Autumnal Equinox then.
During the Classic period, specifically when the ruler who built Temple 22 at Copan (18-Rabbit) was acknowledged as guardian of the World Tree for the people there, the relevant events for the sun's motion along the western horizon occurred in the following sequence in the Maya calendar:
9.13.3.6.8 7 Lamat 1 Mol (February 24, 638 AD: Julian Day #1954142) Accession of 18-Rabbit.
+ 22 days
9.13.3.7.10 3 Oc 3 Ch'en (March 18, 638 AD: Julian Day #1954164) Vernal Equinox at 1:05 AM (local time at Copan).
+ 16 days
9.13.3.8.6 6 Cimi 19 Ch'en (April 3, 638 AD: Julian Day #1954180) Sun setting azimuth 276*49'07" at Stela 10.
+ 4 days
9.13.3.8.10 10 Oc 3 Yax (April 7, 638 AD: Julian Day #1954184) Sun setting azimuth 278*20'24" at mid-line of window in Temple 22.
+ 20 days
9.13.3.9.10 4 Oc 3 Zac (April 27, 638 AD: Julian Day #1954204) Solar zenith passage.
Today, this same sequence of events is virtually unchanged, with only a two-day advance in the Julian dates for each solar position along the western horizon at Copan, which is a result of the effects of the Precession of the Equinoxes. The relevant Maya dates for each position in the Long Count notation are consistent with the fact that the Classic period sequence ended at the zero base-day 13.0.0.0.0 4 Ahau 3 Kankin, as prescribed by its structure, on August 14, 1955 AD (Julian Day #2435334). The following LC notations and CR day-names are calculated from that position:
0.2.6.4.15 6 Men 8 Yaxkin (March 20, 2001 AD: Julian Day #2451989) Vernal Equinox at 7:15:07 AM (local time at Copan).
+ 16 days
0.2.6.5.11 9 Chuen 4 Mol (April 5, 2001 AD: Julian Day 2452005) Sun setting azimuth 276*43'44" at Stela 10.
+ 4 days
0.2.6.5.15 13 Men 8 Mol (April 9, 2001 AD: Julian Day #2452009) Sun setting azimuth 278*18'37" at mid-line of window in Temple 22.
+ 20 days
0.2.6.6.15 7 Men 8 Ch'en (April 29, 2001 AD: Julian Day #2452029) Solar zenith passage.