High Sierra calendar?

I don't believe so. I use Calendar as my main cal application and it works exactly the same as it did before - no added features but it does what it needs to for me.

 

can't go wrong switching to Fantastical. on macOS and iOS.

i myself prefer apple's stock Calendar for macOS.
but on iOS the Fantastical widget screen app is just too good to not use. so on iPhone i have Fantastical installed just to get the widget. at a glance multiple appointments in color in month view.

 

I also prefer the Apple stock calendar for macOS, iPad, and Mac Book. I agree, Fantastical is just too good not use on the iPhone.