Son gets upset belly with fruit when it’s past its best?

WordNet Word definitions in WordNet
n. a date stamped on perishable produce indicating the date by which it should be sold

Longman Dictionary of Contemporary English Word definitions in Longman Dictionary of Contemporary English
noun EXAMPLES FROM CORPUS ▪ But we can be reasonably sure that the drug company will not guarantee the potency of the sample beyond its sell-by date . ▪ Could a turkey with a sell-by date of Dec 27 really be off by Dec 25? ▪ Do women broadcasters have a ...

Wiktionary Word definitions in Wiktionary
n. 1 The final date on which a perishable product can be legally sold to the public. 2 (context idiomatic by extension English) Used to indicate that something, or someone, is old and out of date.