This is the 151st most frequent Finnish word.
päivän
"Päivän" is the genitive singular form of "päivä," meaning "day's" or "of the day" in English.
Here, 'päivän' (of the day) is used in the genitive case, indicating possession or relation.
Tänään on päivän paras hetki.
Today is the best moment of the day.
'Päivän' modifies 'lehtiä,' showing that the newspapers being read belong to or are associated with the day.
Luimme päivän lehtiä aamulla.
We read the day's newspapers in the morning.
Similarly, 'päivän' indicates that the news mentioned are specific to the day, linking it directly.