I get the same results when running the date as non-root user.
Make sure that the "root" user is indeed uid 0 with the id command.
If you are then check permissions and what. Here is my output on a 10.20
system that has no problems changing the date ..

[/home/un410]$ date -u 0416144304
date: do you really want to run time backwards?[yes/no]yes
date: no permission

[/home/un410]$ id
uid=162(un410) gid=25(unix4)

[/home/un410]$ ll /usr/bin/date
-r-xr-xr-x 1 bin bin 16384

[/home/un410]$ what /usr/bin/date
/usr/bin/date:
$Revision: 76.1.1.1 $
PATCH_10_20: date.o 99/03/23

> [~]# date 0416085404
> date: do you really want to run time backwards?[yes/no]yes
> date: no permission
>
> Well, I am root on this machine. If I try using SAM to change time and
> date I don't get an error message but nothing is changed. What is
> going wrong?