Mac calendar menu bar widget Itsycal - free
When working on my Mac, I wanted a menu bar widget that showed a calendar month for quickly referencing dates. I found a great free, open source Mac app called Itsycal.
Itsycal has some useful customization settings. It the ability to add your calendar entries as a list below the month.
Itsycal also has appearance settings that I like. Even the icon in the menu bar is customizable.
I have used Itsycal for years. The developer has kept it up to date and I am currently using it with Mac OS 10.13 High Sierra.

Itsycal on the developer's website.
Free (the developer accepts donations)
Free (the developer accepts donations)
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Added 2018-04-18 <> ID 18041801
Versions - Itsycal 0.11.9
Added 2018-04-18 <> ID 18041801
Versions - Itsycal 0.11.9