This is the 16016th most frequent Polish word.
trzydniowy
Three-day.
The adjective 'trzydniowy' describes the duration of the vacation, specifying that it lasted three days.
Miałem trzydniowy urlop, który spędziłem nad morzem.
I had a three-day vacation, which I spent by the sea.
The adjective 'trzydniowy' is used metaphorically here to imply the age or temporal characteristic of the blanket, as though it has been there for three days.
Znaleźliśmy trzydniowy koc na strychu.
We found a three-day-old blanket in the attic.
The adjective 'trzydniowy' is used to describe the length of the programming course, indicating that its duration span was three days.