[HP Proliant m400] hwclock change won't take effect immediately

So far this issue was only spotted on this specific hardware. And can be seen from kernel 3.13~4.12
Not sure if this is a bug to the software or the hardware.

Test case:
 sudo /sbin/hwclock --set --date "2/2/80 03:04:00"; sudo LC_ALL=C /sbin/hwclock

Expected result:
 * You should see the clock has been changed to 1980

Actual result:
 * It's still showing the current time and date. But if you check it again later (about 1 or 2 seconds) with "sudo hwclock", you will see the updated time and date.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-93-generic 4.4.0-93.116
ProcVersionSignature: User Name 4.4.0-93.116-generic 4.4.79
Uname: Linux 4.4.0-93-generic aarch64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Sep 12 07:55 seq
 crw-rw---- 1 root audio 116, 33 Sep 12 07:55 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: arm64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CRDA: N/A
Date: Tue Sep 12 07:57:28 2017
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lsusb: Error: command ['lsusb'] failed with exit code 1:
PciMultimedia:

ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB:

ProcKernelCmdLine: console=ttyS0,9600n8r ro
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-93-generic N/A
 linux-backports-modules-4.4.0-93-generic N/A
 linux-firmware 1.157.12
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)