This is the 11416th most frequent Russian word.
дневного
"Дневного" means "of the day" or "daytime" in English.
The word 'дневного' is the genitive singular form of the adjective 'дневной', used here to describe the sun's light as pertaining to the day.
Свет дневного солнца освещает поле.
The light of the daytime sun illuminates the field.
In this example, 'дневного' modifies 'отдыха' (rest) in the genitive singular, indicating the rest that occurs during the day.
Во время дневного отдыха я читаю книгу.
During the daytime rest, I read a book.
Here, 'дневного' modifies 'автобуса' (bus) in the genitive singular, specifying the bus operating during the day.