A competitor has two choices for their competition age.
1) They can compete at the age they are on the day of the event.
2) They can compete up to the age they will be during the current calendar year season.
The reason one may wish to go with option "2" would be for points. When you change age and the new age will move you to a new rated division, you may wish to start off the year in that higher age so your points for the entire year will be in the same age group.
A competitor must compete at the highest rank ever earned in the Martial Arts on the day of the event.
State Champ and on Age/Rank Rule
A qualified competitor must compete in the State Championships at the highest age they were on 12/31.
Even if the competitor didn't compete in any event at that age. This is why one may wish to look at how old they will be by the end of the year as they start the season.
One must compete at the highest level earned on the day of the State Championships.