Okay, then what are you expecting to see?
I just set up a test appointment on my work Exchange account with a 5 minute reminder. When the time came (my phone was off with only the "Always On" display showing, it beeped and a small square calendar-like icon displayed just below the clock.
Double-tapped the phone screen and saw the larger white notification bar listing my test appointment; unlocked the phone and saw same in the notification bar. There is nothing in or around the day/time strip.
If you are not getting any of the above, try going to Settings -> Apps & Notifications -> Notifications -> App notifications and check the settings for Calendar.
If you are expecting something different, please elaborate.