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se te cayó una década *
* you dropped a decade
Expression used all the time by Adults
When someone says something that gives away they are not young, something that only people of a certain age would know or be familiar with.
"Cuando era chica miraba Tom y Jerry." "Se te cayó una década."
"When I was a kid I used to watch Tom and Jerry." "You dropped a decade."
8 out of 15 Spanish, Castilian speakers have heard this