It's either aging off or customized. If I want to test some challenges, it's aging off, no matter what the creator says. Since my I had played the decade challenge my settings are these: 1 year = 8 sim days. I didn't changed it after finished the challenged, because they fit perfect to my play style.
Newborn 2 days (0-3 months),
Infant 6 days (3-12 months),
Toddler 40 days (1-6 years),
Child 48 days (6-12),
Teenager 48 days (12-18),
Young adult 96 days (18-30),
Adult 200 days (30-55),
Senior 160 days (55-75 (normal))
In my game I usually switch between several families, so this setting gave me enough time to play the families in the wanted direction and not losing beloved sims too soon.