Lets say programmer want to create timeout (seconds) and want to use max() as default (means never). Obvious (and the obvious (and seemingly only) way to try to do this):

#include <chrono>

void do_work(std::chrono::nanoseconds timeout) {
  /* do smth */
}

int main() {
    std::chrono::seconds my_timeout(std::chrono::seconds::max());
    do_work(my_timeout);
}

Turns out, it IS undefined behavior. Where? In IMPLICIT conversation from seconds to nanoseconds! Timeout in 'do_work' is garbage now!

https://godbolt.org/z/rjqoWr9q4

For me its obvious, that its standard library bug and standard must say what is expected behavior for this