Ordinal numerals in dates

In Czech, expressing dates requires a combination of řadové číslovky (ordinal numerals) and the genitive case.

1. Written Form:
When writing a date using digits, you must place a period (full stop) immediately after the number to indicate it is an ordinal (e.g., 1. means první / first). Standard Czech typography requires a space after this period (e.g., 1. 1. 2024). Note that unlike in English, months in Czech are always written with a lowercase initial letter (e.g., 1. ledna, not 1. Ledna). However, if the numbers are padded with leading zeros (e.g., 01.01.2024), spaces must be omitted. In modern official and business correspondence, the place is written in the nominative without prepositions (e.g., Praha 1. ledna 2024). The traditional locative format (e.g., V Praze 1. ledna 2024) is mostly reserved for personal, private, legal, or historical documents. Adding the word dne (e.g., V Praze dne 1. ledna 2024) is highly formal and bureaucratic; while highly customary and traditional in legal contracts, police protocols, and official state documents, it is not a strict requirement. In modern business contexts, the ISO date format (YYYY-MM-DD) is increasingly common. When using this descending format, Czech typography uses hyphens instead of periods and omits spaces (e.g., 2024-01-01).

2. Spoken Form & Morphology:
When answering the question Kdy? (When?), the day is in the genitive case. If the month is expressed as a word, it is also in the genitive case. The day takes the adjectival ending -ého for hard adjectives (e.g., 5. = pátého) or -ího for soft adjectives (e.g., 1. = prvního, 3. = třetího). The month takes its genitive singular ending, usually -a or -e (e.g., květen → května), with the notable exceptions of listopad (genitive listopadu) and září (which remains září). For compound ordinals (21st–31st), both parts decline into the genitive (e.g., 25. becomes dvacátého pátého), or they can be read as a single word (pětadvacátého). If the month is written as a number, standard Czech requires both the day and the month to be in the genitive (e.g., 15. 7. = patnáctého sedmého). Reading the numerical month in the nominative (e.g., patnáctého sedmý) is a widespread colloquialism common in informal spoken Czech, but it is not considered standard. In formal contexts, reading the month as a word in the genitive (patnáctého července) is also standard. In truly informal Common Czech (obecná čeština), the day takes the informal ending: patnáctýho sedmý (or sedmýho). While the day and month are ordinal and genitive, the year typically remains a plain cardinal number in everyday modern practice. However, historically and in highly formal contexts, the year can also be read as an ordinal number (e.g., 1989 = roku tisícího devítistého osmdesátého devátého). Years before 2000 can be read in hundreds (e.g., 1990 = devatenáct set devadesát) or in thousands (e.g., tisíc devět set devadesát); both are standard and widely used. Years from 2000 onwards are read in thousands (e.g., 2024 = dva tisíce dvacet čtyři). In formal contexts, the year is often preceded by the word roku or v roce (e.g., 1. ledna roku 2024). Crucially, when mentioning only the year (without a day or month), you must use v roce or roku (e.g., v roce 2024). Saying just the bare number or using 'v + number' (e.g., 'v 2024') is ungrammatical. Similarly, when expressing a month in isolation, you must use the preposition v (or ve) with the locative case (e.g., v lednu). Note that when expressing 'on [date]', Czech uses the bare genitive without any prepositions (no 'na' or 'v'). In everyday colloquial spoken Czech, the standard ending -ého is very frequently replaced by -ýho (e.g., pátýho května).

3. Asking and Answering "Today is...":
The case you use depends on the question word. If asked Kolikátého je dnes? (literally 'Of what ordinal is it today?'), the answer must be in the genitive: Dnes je prvního ledna. If asked Kolikátý je dnes? (What date is it today?), the answer must be in the nominative: Dnes je první leden. Note that Kolikátého je dnes? is overwhelmingly the standard and most natural way to ask in everyday speech.

4. Date Ranges:
To express date ranges ('from... to...'), use the prepositions od and do with the genitive case. For example, od 1. do 5. května is read as od prvního do pátého května.