iCloud Calendar events from in my iPhone are not visible on iCloud.com

The title says it all, I have several events on my iPhone, which were added to my iCloud calendars but they are not visible when I log in to iCloud.com.

If I add an event to my Calendar on iCloud.com, the event is visible on my different devices, but if I add an event on my devices, specifically my iPhone, then I don't see them on iCloud.com.

What am I missing?

Thank you!