As a host, you have a calendar on your profile showing when you accept visit requests (open), when you don't (closed), and when you already have a visit planned with WWOOFers (planned visit):
You can "open" or "close" your calendar by editing your host profile:
Currently, you can only open or close entire months of the year, but we plan to allow for more fine-grained configuration in the coming months.
Finally, "planned visits" are automatically populated when accepting a visit request. For instance, accepting a visit request from April 1 to April 16 will mark this period in orange. This lets other potential WWOOFers know that you have already accepted a visit request for this period and either there may be other WWOOFers visiting at the same time or you may be full, depending on your availability.