If you can't see the date of despatch on eBay then look at the receipt you got from the Post Office with the tracking number on it. That'll have the date and time that the item was despatched.
Although I no longer sell on eBay, when I used to sell on the site I always used to keep my receipts for at least a year after the date that the buyer had paid for the item in case of chargebacks, and I always wrote the item listing number, a description of the item and the buyer's name and address on the back of the receipt so that I had something to refer to in case I ever needed to find the receipt and locate the buyer's name and address and find out what the buyer had purchased. With everything written down on the back of the postage receipt that had the date and time of postage on it this helped to keep all of the information in one place.
