capitalization of months and days on calendars

In Spanish we capitalize the initial character of the first word that forms part of a title. Since the name of a month in a calendar page is at the same time its title, then it goes capitalized. The practice of capitalizing the whole title (like in your 1940 calendar) has been dropped.

Month names, day names and season names are not proper nouns and hence, they should not be capitalized, except in the cases that grammar rules demand it and in dates that have a special meaning, like Viernes Santo, 1° de Mayo, Sábado de Gloria, Miércoles de Ceniza.

Thanks, PavkaGuru. So calendars with the first letter of the months and days not capitalized are grammatically incorrect?

Thanks, PavkaGuru. So calendars with the first letter of the months and days not capitalized are grammatically incorrect?

Usually, calendars are very informal and I have seen many of them that not capitalize the name of the month even if it constitutes the title. But I guess that a grammarian will find in it an orthography issue.

Thanks, PavkaGuru. So calendars with the first letter of the months and days not capitalized are grammatically incorrect?

It's not a grammatical mistake. Yes, months are common nouns, and thus generally not capitalized. However, other factors may come into play. If it's considered as the beginning of a sentence, then the first letter of the month is capitalized, as in your second link. Capitalization may also be used if it is considered that caps make the name of the month more legible, easier to read (as in your first link). In other words, it all becomes a question of style rather than grammar.