Expressing Exact Dates
To say that something happens on a specific date, Finnish combines two grammar rules:
- The ordinal number is put into the essive case (ending in -na or -nä).
- The month is put into the partitive case.
Because every Finnish month ends in -kuu (moon/month), forming the partitive is easy: just add -ta (e.g., tammikuuta, kesäkuuta, joulukuuta).
For simple ordinal numbers, you attach the essive ending to the inflected stem. For example, viides (fifth) becomes viidentenä, and kuudes (sixth) becomes kuudentena.
Ordinals from 11th to 19th
When dealing with numbers from 11 to 19, the ordinal ends in -toista (e.g., yhdestoista for eleventh, kahdestoista for twelfth).
When you put these into the essive case, the -toista part stays exactly the same. You only attach the -na or -nä ending to the first half of the word.
- yhdestoista -> yhdentenätoista
- kahdestoista -> kahdentenatoista
- kolmastoista -> kolmantenatoista
Let's look at how to use these dates alongside some common verbs for historical events and milestones.
The Twentieth
For the ordinal number "twentieth" (kahdeskymmenes), both parts of the compound word change. Both "second" and "tenth" must be put into the essive case.
This makes a very long word: kahdentenakymmenentenä! (Remember to take it one syllable at a time.)