There's a way to at least establish when your package enters the tracking system. Unless there's a line longer than 5 or 6 people, I wait at the USPS office and have my item scanned. When they do that, you get a receipt with a date/time stamp that shows when the clock starts. You can do this even if you put stamps on the package rather than using a commercial rate on the postage. Just make sure you put a bar code sticker on the package yourself... there's no charge for this and the USPS will mail you pads of the stickers to use so you have a unique tracking number.