Unfortunately it's not possible to just hide the Date Added from a playlist, but you can make the playlist completely private by right-clicking the playlist and clicking "Make Secret". You can still share the playlist link to people if you want to though 🙂
Let me know if there's anything else I can help with,
The only other solution I can think of is to make a new playlist, put all the songs from your current playlist into it, and delete the old playlist. This way although the date will still show, it'll say they were all added at the same time.
If you have playlist followers you want to keep in your current playlist (Playlist A), just make a new playlist (Playlist B), copy all songs from A into B, delete all the songs from A, and copy them back from B into A.
I would also like to have this feature. I’m reluctant to share my profile with people if they can see the date I added stuff. Spotify please give us a way to hide this from people looking at our profile