/lib/udev/rules.d/85-hwclock.rules is in util-linux 2.29.2-1+deb9u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | # Set the System Time from the Hardware Clock and set the kernel's timezone
# value to the local timezone when the kernel clock module is loaded.
KERNEL=="rtc0", RUN+="/lib/udev/hwclock-set $root/$name"
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