This is the 341st most frequent Serbian word.
оних
The Serbian word "оних" means "those" (genitive or locative plural form).
The word "onih" is used here as a demonstrative adjective to refer specifically to certain days in the past.
Sećam se onih dana kada smo igrali ispred kuće.
I remember those days when we used to play in front of the house.
Here, "onih" functions as a demonstrative pronoun to refer to specific books previously mentioned.
Pročitao sam sve knjige osim onih koje je preporučila profesorka.
I have read all the books except for those recommended by the professor.
In this case, "onih" is part of a genitive phrase modifying the length of time referenced.