DS3231 questions and time accuracy

I have the Pico, and setup an Adafruit DS3231 board with it. I used the info on this page. I am confused about the point:

To set the day. The day is required so that the clocks move forwards
and backwards for daylight saving in the UK. Please note that you need
to call the readDateTime function at least every second for this to
work.

rtc.setDow("day of the week")

At initial setup, I set the Dow to be the day e.g. ("Friday") and set the date and time per that page.

Is setting Dow a requirement? I'm in Australia in a non-daylight saving location. I wonder if setting this is causing an issue I've noticed recently with the time, i.e. when I check the time after running the device & battery-backed RTC over a long period (e.g. 3 days continuously) I found the time is one hour out (shows one hour earlier than the true time). Has anyone else seen this issue?

Thanks,

Michael.