bool summertime (int year, byte month, byte day, byte hour, byte weekday, byte tzHours); when using this library. It appears that there is some change in the use of the type byte. I re-tested with ...

I am posting this issue here first as I am using Arduino-Pico, but this could well be an issue in the underlying Pico SDK or even a hardware issue. I am going to do further testing but I will describe ...