I've only recently started using a calendar to keep track of my personal schedule (the same way it is normal to do so for one's work schedule). I would like more tools like this to make it more convenient than manually adding everything (though ideally using .ics rather than Google Cal). Either via third party tools or companies allowing you to download .ics files from them.

Flights are an area this would be particularly handy; some airlines allow you to download flight reservations as .ics files, but very few in my experience. I looked into making a script to do this in Python before (based on confirmation emails) and while it would be quite doable, the lack of consistency in how the emails are formatted and the airports are described makes it non-trivial (if you want to properly handle timezones).