This'll prevent us from having to iterate over all million-and-a-half minutes since the app was born, while still having some record of the past (which might be useful for other types of analytics down the road)

So, we pass in a time that's over a month ago, it only creates 'day' summaries, over a week ago only 'hour' summaries, and otherwise [if the times are recent enough] we get the full minute summaries.