Don't even really bother looking at the date. If i smells bad, it goes, if it doesnt, I eat it.
I bought some milk a while back for a weekend trip I was going on. In the end I didn't use it, as I stole someone else's, but it went in the fridge when I got home along with the other one that was already open. 4 weeks later, It was still there and I thought I better use that soon... I forgot.. Another week later I finally get around to opening it. Gave it the sniff test, smelt fine, drank some... no problem.
Looked at the date and I noticed its use by date was actually the date I went away on the trip! So Milk can easily go a month past its "use by" date.
Ive had 3 year old bitter before, no issues.
2 year old crisps, bit cardboardy, but edible.
Our ketchup has 2012 on it, still going strong.
Found a tin of all day breakfast in the cupboard about two weeks ago, 2011 date.. Tasted as good as a tinned all day breakfast can.
I think my oldest item was a ration pack from an ejector seat out of a 1960's jet.. It had some chocolate and some soup, plus some weird boiled sweet type things, none of which tasted great, but Im not sure they would have when new TBH. So 40 years old or so past its expected life.