Hi,
The dates in a table do not specify when an item changes rules level. They simply indicate when an item is prototyped (if it is still in the prototyped phase, you get a year ending in "P"), or goes into mass production (no "P"). Advanced and Tournament Legal items are in production, so the date stays unchanged even when they move from "advanced" to "TL".
The change in level is considered effective with the period covered by the whole table.
Thanks,
- Herb