Try our product Clappia (https://clappia.com).
You can get the users to upload their files, answer certain questions and then download the responses in the spreadsheet.
Bonus: They work offline if used through the apps.
It depends what your willing to do, and what software your web page is using.
There is a Google API, and specifically a Google Calendar API.
Your python script can now independently read and write to your or any calendar you have ...
I think Django is a good framework for realize this project.
It's a special Python Web Framework. You can directly create and administrate you're Database with code (look around models).
There is some special functions for create forms, views, GUI...
Moreover, you can use all library from Python like MatPlotLib for your charts or Bootstrap for you ...
I make my own loggers using Google Forms. Each time I submit something, it is saved to a spreadsheet with a timestamp, and I can customize what data I log each time. I use it for weight log, symptoms log, cat weight log, etc. and can generate charts inside the Google Sheet it produces.
I don't have to worry about proprietary data formats or the app ...