This is the 719th most frequent Estonian word.
jaanuaril
"Jaanuaril" in English means "in January" (adessive case of "jaanuar").
In this sentence, 'jaanuaril' is used in the adessive case (characteristic in Estonian grammar to indicate 'on a specific date'), combined with 'esimesel' to express 'on the first of January'.
Esimesel jaanuaril tähistame uue aasta algust.
On the first of January, we celebrate the start of the new year.
Here, 'jaanuaril' is again in the adessive case, pointing to a specific date in the month of January, combined with 'kahekümnendal' for 'on the twentieth'.
Kahekümnendal jaanuaril toimub tähtis koosolek.
On the twentieth of January, an important meeting takes place.
The use of 'jaanuaril' in this sentence adheres to the adessive case role, marking the specific date referenced with '15.'