What calendar app do you use the most and what do you like about it?

Calendly is still my main, purely because I haven't found a strong enough reason to switch

I used Outlook for work but Calendly for personal projects has been good.

Well maybe Morning Bird. This app is so underrated among the niche of calendar tool :( Thanks to its functions, I'm able to handle well my daily to-do-list. I find it allows users to catch up with other's users calendars if they open to public. Here's where I explore it: https://morningbird.io/