Actual food? Probably yogurt at like one or two months. It had been sealed up until then.
I've had table syrup that was at least 4 years past the expiration (it actually still had the aunt Jemima on the bottle is how old it was).
A few days ago I finished some baking powder and my partner brought a big bottle home and I was like "oh it's okay that stuff doesn't expire!" Then I looked at the previous container I had and found out it had, in fact, expired in 2017. Don't think it affected my baking though.
I mostly just eat stuff without looking at the dates unless it smells bad or is moldy.
I am trying to get diagnosed as an adult and recently reached out to my parents for symptoms from when I was younger as those are necessary for adult diagnosis. My mom had pretty much the same reaction as you when I went over the symptoms. Lol ADHD is genetic.