Hi Daniel,
My name is Cody, and I’m an engineer at Webflow.
I’m curious exactly what you mean by “integrate inside Webflow E-commerce”? Can you elaborate a bit more on exactly what sort of integration you had in mind in the context of E-commerce? For example, are you asking if a product can use a calendar input in some manner?
If you simply mean integrate a jQuery plugin into webflow than most any jQuery calendar plugin can be integrated inside Webflow regardless of if you building an E-commerce site or not.
You can read more about integrating jQuery plugins here: Webflow.js and jQuery plugins & here Custom code in head and body tags | Webflow University.
Also, depending upon your needs you could also just implement a native calendar. <input type="date"> - HTML: HyperText Markup Language | MDN. But this would require a custom code embed and the browser support is limited. (e.g. http://webflowdatepicker.webflow.io/)
Please let me know if this is helpful or if you have any additional questions.
I’m happy to help further!
My Best,
Cody