But how critical is it that all these systems have the correct time? Mostly, this won't be that big of a deal. So what if some ancient device thinks it's 1970?

But how critical is it that all these systems have the correct time? Mostly, this won't be that big of a deal. So what if some ancient device thinks it's 1970? Most of these devices don't even have UIs to set the time correctly: so they might have never had a correct notion of time to begin with. And how many of these devices have an uptime of 68 years? What happens when you turn these things off and on again? Do they start out at 1970? If not, where do they get the correct time? Embedded devices don't come with internet connections so there is no ntp running on them. Probably banks and insurers with ancient software might have to patch a few things up again. They would care about having a correct time representation. But they still have 15 years to figure that out. And at this point, you'd hope they'd be aware of this at least.