Dates and Years

An Esperanto date normally presents the ordinal day, then de + month, then the year: la dudek-oka de Septembro 2026. The structure is transparent once you restore the often omitted nouns: la dudek-oka tago de Septembro de la jaro 2026. The day is ordinal because it occupies a position in the month; the year is commonly a numbered label.

The main difficulty for English speakers is not forming the numbers. It is choosing the correct case for the date's role and resisting month-first or ambiguous all-numeric formats.

The basic day–month pattern

Use la + ordinal + de + month. The noun tago is normally understood and omitted.

The -a on dudek-oka and dekunua is the adjective ending: these forms modify the understood tago. The preposition de is essential because the ordinal belongs to the day, not directly to the month. La unua Majo would suggest the first of several May months rather than the first day of May.

With digits, write the ordinal ending after a hyphen: la 1-a de Majo, la 23-a de Novembro. A simplified printed form such as 1 Majo occurs, but it is still read as la unua de Majo. Writing -a makes the Esperanto grammar visible and is the clearer pedagogical choice.

Case depends on the date's sentence role

A date is not automatically accusative. As a subject or a predicate identifying the date, it has no -n:

When the date answers kiam? “when?” without a preposition, it commonly takes temporal -n. The understood form is la dek-kvaran tagon:

This is a minimal role contrast: La sesa de Julio estas dimanĉo has a subject date; Mi alvenos la sesan de Julio has a temporal date.

After an ordinary preposition, that preposition already marks the role, so do not add temporal -n:

See calendar dates in the accusative for the full case contrast.

Adding a year

The full transparent structure is la + ordinal day + de + month + de/en la jaro + year:

In ordinary dates, de la jaro is often omitted: la 18-an de Aŭgusto 2024. When mentioning the year separately, en la jaro 2026 is completely explicit, while en 2026 is common and concise when no other numbering system could be intended.

The written year is usually digits. Two readings are established:

• a cardinal-style reading: 2026 = du mil dudek ses;
• an ordinal-style reading: 2026-a = du-mil-dudek-sesa, with understood jaro.

PMEG records the ordinal reading as traditional but comparatively uncommon today in fully spoken year expressions; cardinal reading is also attested from Zamenhof onward. For learners, the cardinal reading is transparent and internationally easy to process. The ordinal remains correct when the sentence explicitly conceptualizes “the 2,026th year.”

Month names and capitalization

The traditional and PMEG-recommended analysis treats month names as proper names: Januaro, Februaro, Marto, Aprilo, Majo, Junio, Julio, Aŭgusto, Septembro, Oktobro, Novembro, Decembro. They therefore begin with a capital and normally appear without la.

Lowercase month names are also attested in contemporary publications and reflect a more general lowercase-oriented style. Capitalization is not fixed by an inviolable grammatical rule in the way case endings are. For a consistent reference standard, this guide follows the foundational examples and PMEG recommendation: capitalize the standalone month name, but lowercase an ordinary derivative such as januara.

The adjective januara is lowercase because the derived adjective is not itself a proper name.

Numeric dates and international clarity

Forms such as 4/5/2026 are dangerously ambiguous: an American reader may see April 5, while many others see 4 May. In international Esperanto communication, either spell out the month or use the ISO 8601 order YYYY-MM-DD.

ISO formatting is a (formal/technical) convention rather than an inflected Esperanto phrase. Do not pronounce the separators mechanically; expand 2026-05-04 as a normal date. The international standard is a strong recommendation for databases and cross-border forms, while the written-out month is often friendlier in prose.

A letter heading traditionally behaves like an implicit “written on...” time phrase and can carry -n:

Both the weekday and the day ordinal take temporal -n in this (formal) standalone date line.

Decades, centuries, and ranges

A decade may be written la 1990-aj jaroj, literally “the 1990s years.” The adjective ending and plural -j attach to the digits, and jaroj makes the unit explicit.

Centuries use ordinals because they are ordered periods: la dudek-unua jarcento. The adjective agrees if its phrase changes case.

For a year range, an en dash is appropriate in compact (formal/technical) writing: 2026–2028. In speech or ordinary prose, expand it as de 2026 ĝis 2028. Do not combine only half of the two systems, such as de 2026–2028.

Dates are not durations or clock times

The calendar date uses an ordinal day; elapsed time uses cardinal units; a clock hour uses an ordinal with a preposition:

Here la duan is a temporal date, je la naŭa is a clock time, and tri monatojn is measured duration. English can use the same preposition “on/at/for” patterns less systematically; Esperanto marks the three relations differently.

Common Mistakes

Copying month-first English order

Using a cardinal day

Adding -n after a preposition

Putting case on the month

Using an ambiguous all-numeric date internationally

Key Takeaways

Build a date as la + ordinal day + de + month, adding the year afterward. Let the date's role determine case: no -n as subject or predicate, temporal -n when it directly answers “when?”, and no temporal -n after a preposition. Capitalize standalone month names in the reference convention used here, read years transparently, and avoid national numeric formats that an international reader can reverse.