I'm curious what benefits you see something like this offering over a more "full-fledged" collaborative trip-planning solution like https://wanderlog.com/? The benefits of a full-featured travel-planner outweigh a calendar, especially when it does things like automatically calculate the driving time between stops. Other travel partners can "like" things, create new "lists" for whatever ("possible hotels", "restaurants", "attractions", etc.) and then drag them down to specific days. And you can "share a link" to the trip for others to just view, or invite others to collaborate...