Invited to Birthday Party with Unplayed Aging OFF?

I've had this one. I think it is a bit of a random event. The few I've had were all YA and only age up if you actually use the cake at the party... or rather that's what I assume since the only one I didn't send to the cake didn't age up. Maybe I got lucky there.

I always assumed it was because aging is off so it presents an opportunity to you here and there to age up a townie. I usually don't attend them though.

Thanks. If it’s a random event, triggered by aging off for a time and has no effect in the long term -that’s great. :)
I am playing a rotation and unplayed Sim aging is only one week out of four.

It doesn’t effect the townie sims age either from my experience. I moved a townie sim into one of my household, and this townie knows quite a few of my other sims. I was playing a different household when a bday invite from this particular townie showed up via ph call, I didn’t accept, but I saved my current household to check on the townie. The townie hadn’t aged up.

I had this happen, but it was a played sim in my rotation and yes she did age up. I had to cheat and age her back down.