Q: Calendar app does not remember/display my appointments

I've an iPhone 6+ running iOS 9.3.5. When I add an appointment to the calendar it acts like it does not remember the data. If I open the day again no data is displayed for the entry. On the month screen a gray dot is not under the day date.

However, the info does synch to my Calendar app in OS X (10.11.6). So it appears as if the data is on the iPhone, but will not display on the calendar day page.

What's wrong?

Thanks,

Bill