They used to be date-coded just like motor vehicle tires, with a four-digit code designating the week and year (last two digits).

I'd already noticed that they've stopped doing that, which is disappointing.

I think the crossed circle and the following digit is the new date code, but that's totally a guess. If this is correct, I'm guessing that the dots inside the circle represent the month, and the single digit represents the year.

It seems to jibe with the tires on my bike now and the couple of old ones I have lying around.

But I'd want to hear that from Conti (or know that it's a new standard for bici tires) before I'd rely on it.