"Back in the day" is a popular expression and one that can be used to imply a wondrous, happy time, before a mortgage and kids turned your hair gray, and when disco was the favorite flavor of Michael and his lovely brothers; or it can be used in a sort of depressing and passively aggressive way, such as: "Back in the day we didn't even HAVE cell phones," and it always smacks of the old "I walked seventeen miles to school in the snow, without shoes!"
But back in the day needs to be used with great care. I can remember hearing about how back in the day women didn't have the right to vote and were discouraged from working outside the home; some of us may discuss this with the inherent understanding that these were archaic, profoundly offensive norms. However, others of us discuss these times with longing. How offensive to sit with someone harkening back to the days when women were still viewed as so much livestock in a winsome, melancholy manner?
On the other hand, you may learn a lot about someone by listening and not reacting, knowing that their personal "back in the day" may or may not be a place you would want to visit.
Aimee Boyle is a teacher, mother, wife and writer. She is a regular contributor to EmpowHER.