July 2020
I had the exact same issue after installing Island Living. No custom content, nothing special. Just games and expansion packs. I’ve spent four days alive as a sim on long aging and it already has me aging up to adult in 71 days. Each day my sims age 2-4 days. I’m so bummed because I didn’t notice and now if I spend extra time at university, my Sims entire young adulthood will be over unless I turn aging off completely, which then impacts his girlfriend (who I haven’t been playing) who is now 17 days younger than him.
February 2021
I've got this issue now, did you end up fixing it?
February 2021 - last edited February 2021
I had this issue at least twice recently. I had twins that were born in game in game, thus sharing their birthday. Suddenly I noticed that other sibling’s birthday was only a few days ahead whilst the other one had still several weeks until his. Somehow the sister aged faster than her brother.
I also have a toddler sim. Her mom became pregnant and on the same sim day I checked when would the toddler’s birthday be and she had still 3 full sim weeks of toddlerhood left. So, on the same day the mom sim gave birth I checked the calendar again and noticed that the toddler would age in 7 days! So in the 3 days her mom was expecting the toddler aged full 2 sim weeks.
edit: I also have an elder who won’t age. At all. She’s permanently stuck in day 1 of elderhood. Changing the life span settings won’t do anything. Taking her into CAS, making her an adult again and aging her back also won’t do anything. She’s not a spell caster or a vampire, just a regular sim. She aged normally until she became an elder. Her husband died ages ago.
May 2021
I've been experiencing this as well. I've noticed it only happens when I have "age unplayed sims" toggled off.
August 2022
I had this problem in one of my saves. The only thing different about that save is a double of my sim showed up at a school function and I deleted the sim. I'm not sure if it was the doubling or the deletion of the double that did it but that sim, now ages two days every day.