Some PC based applications such as the built-in calendar, mail and other applications can connect to web-apps in order to show your online calendars in a system native, and therefore more intuitive, view.
Those applications would definitely be on-topic on Super User and to help narrow down where the problem lies it can be beneficial to know where those applications are getting their data from, especially if it is a third-party service or web application.
If you read the help center you will find a similar exclusion for android and ios smartphones that states they are off-topic:
- electronic devices, media players, cell phones or smart phones, except insofar as they interface with your computer
The same applies for web applications, they are off-topic unless the problem is explicitly focused around your computer or web browser program. How to actually use the web applications belongs on the relevant Stack Exchange site: Web Applications.