Yes, Howbout is a shared calendar app built for friends.

Howbout makes it easy to organize plans with friends. You can see everyone’s availability, plan your hangouts and meet ups, add all the event details, and chat in every plan, all in one place. It’s the easiest way to keep your social life organized and stops details & planning from getting lost in group chats or forgotten. Howbout helps you make plans that actually happen.