I have a time stamp that shows me when a user logs in to their account online. I want to analyze how often people log into their accounts on average, for different demographic groups. What I want is to say, "this group logs in every 6 days and this group logs in every 4 days". Also, "a year ago people logged in every 10 days and now they log in every 5 days... "etc.
My question is how to calculate the time difference between each log in record. Since it's one field, I don't think I can use datediff.