Notification system for calendar events and reminders

I think through gcal-cli you could probably make an action handler for the datetime module that would get recent reminders and then put them in a little window (similar to system tray).

Making calls to gcal-cli might be slow, so maybe set up some sort of cache?

Start by examining the datetime module and how gcal-cli is invoked; the issue does not name a file or test. Define the action handler's reminder and caching behavior before implementing a system-tray-like window, with completion meaning recent reminders are displayed without relying on slow repeated calls.

Written by the indexing model from the issue text.