There is little use for monthly calendars in SharePoint when everyone has an exchange outlook calendar...so what do we need on a shared basis? Resources! People, vehicles, rooms, accommodation, equipment, rentals.......and the only way to achieve this in the SP calendar app is by overlaying everything into tiny squares on a monthly grid, ridiculous! What we wan't is the ability to append resource calendars as rows or columns with dates horizontally or vertically.
Dori Willard commented
Not only that, articles say you can do it for SharePoint Online: https://support.office.com/en-us/article/Use-a-Group-Calendar-7F559B2E-1F90-49B4-A0FE-2D235994945E