Anywhere past 40. At 27, barring some unrelated issue, you’re capable of ascertaining what you want in a partner.

Edit: now, if you had met them before they were in their 20s, it gets a bit weirder but not much. If you met them as a kid, it gets substantially weirder.

~~_Nope. 80 year olds dating 47 year olds is fine. They are both adults.

Bit sketch on the low end though. People younger than 30 don't know anything._~~

I misread. Once being a teenager is hard to remember for the younger person. Certainly by 40.

It's probably going to depend on the two people and their relationship. If they get hung up on their past experiences being different, then it won't work well. If they have similar likes and goals now and that's what the relationship is about, then the age difference probably won't be a factor. There are plenty of people of the same age or off by a few years that don't get along at all.

Let's analyze.

2X - (X+7) = 13

Solve for X=20. So 40 and 27.

That's the lower limit of the rule that says it's okay. Is it weird for a 40 year old to date a 27 year old? I'm going to say no. At 27, you're an adult and you've been an adult for awhile. At 40 you're not quite, but close to middle aged. Both are kinda in the ballpark age-wise, just on different ends.

As you get older, that 13 year gap is going to feel even smaller.