The words equinox and solstice refer to four specific days in the year—one in each of the four seasons. ... The summer and winter solstices occur in June and December. These terms are not capitalized.

Should autumnal equinox be capitalized?

Don't Capitalize Terms Like 'Spring Equinox' and 'Fall Equinox' And the names of all these significant astronomical days are all lowercase. You don't capitalize terms like “fall equinox” and “summer solstice.” The solstices, by the way, are the opposite of the equinoxes.

Is equinox a proper noun?

Guideline 1: Lowercase general references to seasons, solstices, and equinoxes unless they start a sentence. ... Let's go hiking in celebration of the autumn equinox! Guideline 2: Capitalize references to seasons, solstices, and equinoxes if they're part of a proper noun.