The machine.RTC documentation has some discrepancies.

The ESP8266 machine.RTC modules doesn't appear to have an init function, but rather has a datetime function.

The order of the arguments to datetime appears to be (year, month, day, wday, hour, minute, seconds, milliseconds)

The ESP32 machine.RTC module

has an init function and a datetime function. The order of the arguments for datetime and init appears to be (year, month, day, hour, minute, seconds, microseconds)

The stm32 machine.RTC module forwards to pyb.RTC

which has an init function and datetime function, but the init function doesn't take any srguments. The datetime function appears to use the order (year, month, day, wday, hour, month, seconds, microseconds)

The documentation documents an init function with arguments in a different order to any of the above and doesnt't mention a datetime function.

And the EPS8266 appears to take milliseconds as the last argument, whereas the others take microseconds.