http://savemytime.co/ does tracking like this very well with replacing the lock screen with a time tracker, how are you going to collect and categorize user's time? Every time tracker I have tried never stuck with me until it was in my face, all the time.
Wouldnt it be easier to use a dedicated app for that, like "SaveMyTime" ( http://savemytime.co )? This app allows you to input data every time you unlock your smartphone. To be honest I never used it, but it simply sounds much better than using some spreadsheet. There are probably other apps that do it too.
I think you will have to buy the app to be able to export data to Excel, but its probably worth it