Some calendar/schedular/workflow assistants I launch for clients will be tailored for their specific needs. Some clients will need more complex systems to accommodate their customers, others won't (and those can use the general scheduler). You can limit the number of appointments you want each day, toggle daily avaiability, and even send notifications to customers to confirm their appointments.
For the individually tailored schedulers, I always like to start with a conversation. Sometimes, business owners are themselves unsure of exaclty what sort of scheduler might be best at any given moment. Not enough designers and developers are willing to actually sit down and talk with the owner to get to know them and, more importantly, their business. Everyone has their own idea of a "system," and that's what I aim for, the business owner's concept of what kind of scheduling app they need. The good news is, the application can grow with your business.
For the curious, I've offered a free trial of my basic scheduler, up to ten appointments per day, five days per week, set your appointment intervals, with an admin login dashboard link to your own website or social media page for convenience.