This is a record of my code to use an old Pi-3 and an even older EVGA monitor to make a clock for my home office showing the time and date and the next five entries from my Google Calendar.
The works of clock.py are copied straight off the google API website with a file output added so you'll need to read up on getting your developer credentials but it is free and quite straightforward.
I commented all the C++ code in ELI5 style so I would have a quick gtkmm example to go to for future projects. Also I included the command line argument handling stuff and implemented the button/timer functions as lambdas which might be a bit OTT for a simple clock.
The only annoyance is that the Google user token only lasts about a week. I suspect this can be fixed but haven't bothered yet. Most of the commits are me tweaking the spelling...