Since we were getting low latency data inside HTTP responses we could work off of the response header clock skew to narrow origination time down to around one second, and that’s almost as good as NTP can manage anyway.

As RPC mechanisms go, HTTP is notable for how few of the classic blunders they made in 1.0 of the spec. Clock skew correction is just my favorite. Technically it exists for cache directives, but it’s invaluable for coordination across machines. There are reasons HTTP 2.0 waited decades to happen. It just mostly worked.