Don't kid about this, smamurai. Everyone knows that bottles, like socks*, go backwards in time. The sell-by date is the maturity date on the bottle. Beyond that date (in our reference frame -- before it in the bottles'), the bottles have not yet reached the required level of stability.
* -- That's right. Consider how when you see yourself putting two socks in the washer, and only getting one back out, what has really happened is that the backward-flowing sock has reproduced.