CAPITAL LETTERS (Majuskloj).
70. Capital Letters (Majuskloj) may be used as they are in English, but as their use varies in different languages, it is as well to follow the majority of Esperanto writers. We, therefore, advise the student to—
Use capital letters, as in English, except:—
(a). For words derived from the names of places, as:—La angla nacio = The English nation. Li estas franco kaj loĝas en Francujo = He is a Frenchman and lives in France. Sur la danan tronon mi havas rajtojn = On the Danish throne I have rights.
(b). For the names of the days of the week, as:—Mi alvenos lundon = I shall arrive on a Monday.[12]
(c). For the pronoun "I" = mi.
In the Fundamento, Zamenhof used capital letters to begin the names of months. In his mature style he also used capitals for nouns and adjectives of nationality, e.g. Angla, Anglo, Dana, Franco.
Footnote:
[12] Note that lundon means "on a (or, some) Monday." If we wish to say "on Monday," meaning "next Monday," the full translation would be Mi alvenos la proksiman lundon = I shall arrive on (the next) Monday (see par. [68] (b)). Mi venas lunde = I come on Mondays.