What is a 60/40 dance?

I think they might be referring to a style of dance that was popular back in their day.

Wouldn’t it make sense to ask them when they’re talking about it?

Seems to refer to swing dancing.

This is the only definition for a 60/40 dance that I’ve heard. The men are around 60, the women are around 40.

@Jeruba I’m assuming the OP’s parents are passed, otherwise, I’m confused as to why he doesn’t ask them.

@AshlynM, “My parents often tell me” is present tense, which implies that they’re still living. If the OP had said “told me,” then I would draw the same conclusion you did.

It refers to the percentages of the style of dance which will be played during the evening. A 50–50 dance night is 50% modern dances and 50% old-fashioned. A 60–40 dance has more modern dances, thus appealing to the “younger” people.