How you view the age of the earth -- 49,000 years or less vs billions of years -- will depend on how you view Day 1 of the creation.
I. Some people feel that Day 1 included the creation of the heavens and the earth, and if each creative period is 7,000 years long, the earth would have to be no more than 49,000 years old. This web site lays out the Days this way, https://www.calvinseminary.edu/worship/artwork/creationDays.php.
II. Others feel the heavens and the earth were already here when the 7 creative periods began, so Day 1 begins with creating the light. This allows for the heavens and the earth being much older than other created things.
That's how this web site shows it, http://www.bibleview.org/en/Bible/Genesis/7Days/
The WTS takes the second point of view, light was created on the first Day. This chart is from the Insight book, p 527.
Leolaia's excellent research shows that the Society has no problem accepting that the earth could be billions of years old, which their view of Day 1 of creation allows for.