Check the purchase invoice or receipt
Check the warranty start date on the manufacturer’s website
Look up the IMEI on the carrier’s warranty or activation portal
Contact your mobile carrier and ask for the activation date
Check your account history in the carrier app or website
Review the device’s original box or activation paperwork
Use the phone’s IMEI to request activation details from the manufacturer
Check the first service date in your carrier records
Search your email for the activation confirmation message
Visit a service center with the IMEI and proof of purchase