Where do they get the data? I just checked mine and have nothing for the last 30 days. But I only sparingly log in to Google in an incognito window, don't have

Where do they get the data? I just checked mine and have nothing for the last 30 days. But I only sparingly log in to Google in an incognito window, don't have the Google apps on my Android phone, don't use Google Maps much, etc., so I didn't expect anything. Also, does anyone have a good solution for tracking yourself, for purposes like reconstructing the time/date you were somewhere? I used a GPS logging app for awhile, but I don't remember if I ever even looked at the data. I had concerns about battery life, and how to use the data even if I got it reliably and efficiently.