I'm currently using Time.ly for a client's calendar at http://concretecuisine.com. The calendar is pretty customizable from their interface, and is easily implemented in the Webflow designer. However, there's a cost of $9/month, and it doesn't offer a ton of options for different layouts, since the code is all generated by their interface and not customizable within the Webflow designer.
Does anyone have any recommendations for other tools? I'm guessing this would be possible with the CMS API, but this client isn't using any other CMS features so I'm not sure if that's the best route right now or not. Hope to hear from all of you!