Seasonal Date Pairs

Seasonal Date pairs are days that exhibit the same Sun path in the sky (same number of days from nearest Solstice.) For example, Apr10 and Sep01 are date pairs (both 72 days from Summer Solstice.) For both of these days at 33deg north latitude, when the Sun is at 270deg azimuth it's also at 15deg elevation.

DOY (day of year)

Equinox (Spring)
081 (W +91, S -91) Mar22 (33deg north Sun: 260.6deg azim 15deg elev)

Closer to Solstice (Summer)
082 (S -90) Mar23 (day after Equinox)
...
100 (S -72) Apr10 (33deg north Sun: 270deg azim 15deg elev)
...
125 (S -47) May05 (33deg north Sun: 280deg azim 15deg elev)
...
172 (S +00) Jun21 (33deg north Sun: 288.6deg azim 15deg elev)
...
219 (S +47) Aug07 (33deg north Sun: 280deg azim 15deg elev)
...
244 (S +72) Sep01 (33deg north Sun: 270deg azim 15deg elev)
...
263 (S +91) Sep20 (day before Equinox)

Equinox (Autumn)
264 (S +92 W -91) Sep21 (33deg north Sun: 260.6deg azim 15deg elev)

Closer to Solstice (Winter)
265 (W -90) Sep22 (day after Equinox)
...
286 (W -69) Oct13 (33deg north Sun: 250deg azim 15 deg elev)
...
308 (W -47) Nov04 (33deg north Sun: 240deg azim 15 deg elev)
...
355 (W +00) Dec21 (33deg north Sun: 228.5deg azim 15 deg elev)
365 (W +10) Dec31 (last day of year)
001 (W +11) (first day of year)
...
037 (W +47) Feb06 (33deg north Sun: 240deg azim 15 deg elev)
...
058 (W +68) Feb27 (33deg north Sun: 250deg azim 15 deg elev)
...
080 (W +90) Mar21 (day before Equinox)

Notes
(yes Solstice doesn't always fall on the 21st, but it makes a good average)
(yes Leap Year offsets most of this by 1 day, leap day should really be at the end of the year)