Check the original purchase invoice or receipt
Look at the warranty card or warranty start date
Check the order history in the online store account
Find the purchase confirmation email or SMS
Check the device activation date in the manufacturer account
Use the IMEI/serial number on the manufacturer’s warranty check page
Check the retailer’s customer account or purchase records
Review bank or credit card transaction history
Contact the seller or retailer for the purchase record
Check the mobile’s first setup or activation information if available