Where the date is on a car seat
Federal law requires the month and year of manufacture on the label. Expiration is the manufacturer’s own policy, not a federal rule. That month-and-year is what you're looking for — it's printed on a label on the shell, and the maker's "Do not use after" statement is in the manual or moulded into the plastic near it.
Already found the date? Read what it means for your seat — or go straight to your brand's page for the maker's stated figure.