Specific quota time intervals for Google Calendar API calendar and event creation

I am moving schedule and student statistics of our university to G Suite and Calendar. Every API has strict quotas, so I use a special bottleneck rate limiting library (https://www.npmjs.com/package/bottleneck) to send requests with some computed interval. I managed to find an ideal fast and safe rate for Directory API (460 queries/100 seconds for 1500 queries per 100 second quota). Now I am creating Calendars. There will be more than 2000 of them. If I exceed limit I am blocked for several hours.

The docs suggest that I can only create 60 calendars within a short period of time (https://support.google.com/a/answer/2905486?hl=en). What is this short period of time precise duration? I want to implement my script to run efficiently for both Google and me, as I did with Directory API. If this is confidential, what is the replenishing period?
What different approach can you suggest? I already am going to use multi-user approach.

P.S. Code, that executes the task, in case you want to check it for something: https://github.com/nure-gs-apps/CIST-GoogleCalendarSynch