Alternatives to discontinued Google Calendar Appointment Slots [closed]

Question

On January 4th, Google shut down the appointment slots feature of Calendar. I have been using it intensively, it had just the right set of features for me and now I'm searching for a replacement. Do you know an online appointment system which fulfills the following requirements?

• free
• lightweight: users who want to book needn't create a new account (if one can signup using their Google account, that's also good), fill in forms with multiple pages (like timetrade.com does), or confirm their bookings via email (like scheduleonce.com does)
• there can be multiple calendars (I used it to represent multiple appointment places)
• (optional bonus: booking users can see their calendars during booking to avoid booking time slots during which they are busy)

Answer 1

Now I use YouCanBook.Me with the "On duty events" hack described here. It uses Google Calendar, one can set up multiple profiles (I do it per appointment places I have), and has a lot of configurable options. Since the booking is public, the booking form contains a captcha field, but that is a minor inconvenience.