You cannot.
The only thing you can do is to memorize when you have started to play the game.
The time displayed on your profile on the TEFc site is the time that counts from the day you logged in the community site for the first time, but not for the game.

If you have not played TEF the day you registered, then do not be surprised you are not an adult yet.
Also, keep in mind that you can become an adult earlier or later than expected.
Perhaps you will be an adult tomorrow.
Also, note as well that it counts only from the time you started to play TEF, not from the time you registered.

EDIT: by the way, be patient after you posted.
People may not see your thread the second you posted it. You have to wait at least half an hour or some hours for someone to reply.
(Also, remember that people have different time zones because they live in different countries.)