How to extend the shipping date depends on the Trade Assurance order types.
1. For Trade Assurance orders placed by clicking “Start Order” button on the product detail page, please go to Orders- All Orders, find the order and click “Extend shipping time” on the order detail page to extend the shipping time. 
Note: You can only extend the shipping time when the order is waiting for supplier to ship.
2. For other Trade Assurance orders, ONLY your supplier can modify the shipping date. Please go to Orders– All Orders, find your order, click Request modification button on the order detail page and submit your request. If you have reached agreement with supplier to modify the shipping date, your supplier will modify accordingly. After that, if your order be paid, then you need to confirm the modification on the order detail page, otherwise, your supplier can complete the modification directly.
If there is no reply from your supplier after sending the modification request, you are suggested to contact the supplier directly.