(1) Enable the google calendar API by following step 1 at https://developers.google.com/calendar/quickstart/python
(2) Copy credentials.json to this directory
(3) Install pip packages:
$ pip install -r requirements.txt
$ python main.py
Voila! By default, it computes time spent in all your displayed calendars in google calendar. To override this, you can pass in a list of strings, e.g.
$ python main.py --calendar_names="Reading and stuff","Derping around"