The PCF8563 is currently built as a module in the archlinuxarm odroid-n2 kernel. This prevents the kernel setting the time from the RTC at boot as this process occurs before modules are loaded.
There is a message in the kernel log if you have this issue:
$this->bbcode_second_pass_code('', 'hctosys: unable to open rtc device (rtc0)')
Kernel options need to change to properly fix this. I'm not sure how this affects people without the RTC, but presumably it would do no harm for them apart from a marginally larger kernel.
Fix with new kernel options listed here: https://forum.odroid.com/viewtopic.php?p=275058#p275058