: Check the barcode sticker attached to the back of your physical Xiaomi device or the base of its original retail packaging box.

: When contacting Xiaomi support for repairs or issues, providing your activation date accelerates the process and ensures accurate warranty handling.

On some MIUI/HyperOS versions, you can find status information directly in the settings, though this varies by region. How do I check activation date on Redmi phone? - Blackview

A device activated months before the seller claims purchase is a major red flag for refurbished or used units.