Problem [mac]: recently added songs is marked as songs added months ago

[Hel1ne]

When I add new songs to my playlists and sorting the list by "recently added", some of the songs (not all) doesn't follow the recently added sorting. Usually you can see when the song is added by "5 minutes ago" or the date of the day I added it to the list,  you know. Today I added a new released song to my list, but it says "in 5 months". I now have 30 songs it sasy "in 5 monthts" or "in 8 montsh" etc. These songs is now on top of my list when sortet as "recently added". Some of those songs was added last week, some of them was added months ago. These songs mess up the playlist order. 

This problem only appears on my mac...

What is wrong?