Does one capitalize months of the calendar year in Spanish?
El mes de mayo acaba de pasar. Hoy es el 20 de Junio?
4 Answers
No, the months are not capitalized.
Never capitalize months or days of the week! and if this is a spanish class you are in, the teacher would probably like you to write out viente instead of 20
You can capitilize them only when they are titles on calendar pages, et. al., not in sentences.
Since most people are used to seeing them in minúsculas you often see this:

Yes!
If they start a sentence... ![]()
Octubre ??es mi mes favorito del año.