User data through Google APIs without authorization flow
So, you want to be remembered.
If you want to dispose of any kind of authenticacion but yet the user needs to be recognized you should be using a cookie.
On the server side that cookie should be used to select the offline token.
Of course, without that cookie the user needs to be authenticated in any way. I would make them reauth by Google so you get a new offline token.
Hope that it helps.
I'm writing a web application that reads my personal calendar data, crunches stats, and then spits them out for the world to see. I don't need an authorization flow. Is it possible to leverage the Google APIs without going through a user sign-in flow? In other words, I want my personal Google account permanently and securely signed in to my server without the risk of my token invalidating or having to re-auth.
Right now I'm signing myself in with an offline token, then uploading the authorization file onto my server, basically spoofing the server that I already auth'd. Is there not a cleaner way?  
I've spent hours reading through the API docs and Auth docs, but haven't found and answer. If there is a page I've missed, please point me to it!
PS. I'm using the Calendars API through Python/Flask on Heroku, but that shouldn't matter.