When is a trade-in "initiated" for the sake of the 14-day return window?

Hello! I was wondering, when it comes to initiating a trade-in for a shipped online purchase, when does the 14 day timer on sending in the item to be traded in start? Is it as soon as the purchase is made, or is it from date of receipt? I'm asking because the item I would want to use trade-in credit on would not arrive until roughly 12 days after purchase, and I want to be able to transfer data over before sending the old item in for trade. Thank you!