Times of Day in Cases

In Finnish, time expressions require specific cases depending on whether you are talking about hours, days, or parts of the day.

1. Asking the Time vs. Asking 'At What Time'
When asking what time it is, use Mitä kello on? or Paljonko kello on? (For whole hours, the answer normally uses the basic numeral). When asking at what time something happens, use Moneltako? or Mihin aikaan? (Whole and half hours commonly use the ablative; minute expressions use other patterns below).

2. The Ablative Case (-lta/-ltä) for 'At'
To say an event happens at a certain time, use the ablative case. This ending is used for whole hours and half-hours. Note that the ablative case is almost exclusively used with the 12-hour clock (numbers 1-12). While the ablative is the standard textbook rule, using the nominative for whole and half-hours to mean 'at' is also correct and very common in everyday speech (e.g., Tulen puoli kuusi). The 24-hour clock typically uses the nominative case even to mean 'at' (e.g., Tapahtuma alkaa kello neljätoista = The event starts at 14:00), rather than requiring an ablative ending. When expressing minutes past or to the hour, the ablative is not used on the minutes; instead, the hour is in the nominative or genitive.

• kello viideltä = at five o'clock
• puoli kahdelta = at half past one (literally: at half to two)
• kymmenen yli viisi = at ten past five
• varttia vaille kolme = at a quarter to three (using vartti in the partitive case)

3. Yli, Vaille, and Puoli

• Yli (past/over): Used for minutes past the hour. Both kymmenen yli viisi and kymmentä yli viisi mean ten past five. The hour can also be genitive: kymmenen yli viiden.
• Vaille (to/lacking): Used for minutes to the hour. Both the nominative and partitive minute amount are standard: viisi vaille kuusi and viittä vaille kuusi (five to six). Vailla is an equally acceptable alternative to vaille.
• Puoli (half): Warning: In Finnish, puoli counts FORWARD to the next hour. Puoli kolme means 2:30 (halfway to three), not 3:30!

Genitive Hour Variant
Nähdään viittä vailla kuuden and Nähdään viisi vaille kuusi both mean “See you at five to six.” The minute case and the hour case vary independently.

4. The Translative Case (-ksi) for 'For'
To say something is scheduled for a certain time, use the translative case.

• Varasin ajan kahdeksi. = I booked an appointment for two.

5. Days and Parts of the Day
Finnish uses different cases for broader timeframes:

• Days: Use the essive case (-na/-nä). E.g., maanantaina (on Monday).
• Parts of the day: Use the adessive case (-lla/-llä). E.g., aamulla (in the morning), illalla (in the evening). However, when modified by words like 'this' or 'last', they switch to the essive case (-na/-nä). E.g., tänä aamuna (this morning), viime yönä (last night).

6. Inflectional Stems
When adding endings, numbers use their vowel stem. For numbers 1, 2, 5, and 6, this stem also uses the weak grade of the consonant:

• yksi → yhde- (yhdeltä)
• kaksi → kahde- (kahdeksi)
• viisi → viide- (viideltä)
• kuusi → kuude- (kuudelta)

For the number 7, the vowel stem is simply seitsemä- (seitsemältä), without undergoing consonant gradation. For numbers 11 (yksitoista) and 12 (kaksitoista), only the first part of the compound number inflects, while the element '-toista' remains unchanged (e.g., yhdeltätoista, kahdeltatoista).