Hardware and System clock both wrong in linux

So your UTC time is about 17 minutes off.

System clock synchronized: no NTP service: active 

Although the NTP service is active, the System clock synchronized: no indicates it has not succeeded in getting accurate time information from the NTP servers it may be configured to contact.

You should look at the status and configuration of the actual NTP service. It might be literally ntpd, or chronyd, or systemd-timesyncd. (Note that systemd-timesyncd is a SNTP client, unlike the other two, which are both full-featured NTP clients.)

To query the status of ntpd, use ntpq -np.

If you have chronyd instead, use chronyc -n sources

For systemd-timesyncd, use timedatectl show-timesync --all.

The outputs of these commands should reveal if the NTP synchronization service is configured with any NTP servers, and if it has managed to contact any of them. I'd expect that you'll find that either no NTP servers are currently configured, or that the server has failed to reach them.

The configuration of ntpd is typically at /etc/ntp.conf, chronyd's is at several files and sub-directories in /etc/chrony/, and systemd-timesyncd is configured at /etc/systemd/timesyncd.conf.

Since your system clock is so far off the real time, the time synchronization servers might fail to sync it automatically, in order to avoid large time jumps. If so, you might have to start the synchronization manually once with an appropriate option to allow large time adjustments: for ntpd, it would be ntpd -qg.

Due to this, my hardware and system clock both show the wrong time.

Hmmm. That seems unlikely. However if the other OS was MS-Windows, that might explain some of the disparity. When PCs shipped with MS-DOS (or even DR-DOS) the hardware clock was set to local time / MS-DOS didn't understand timezones. The ghost of MS-DOS is still present in modern MS-Windows - which can be configured to keep the HW clock in sync with the local timezone or in UTC. However since your computer appears to only be out by 15 minutes, it would appear that your other OS was using UTC on the hw clock.

OTOH you have tagged this with "arch-linux" and say you installed EndeavourOS - so presumably both OS are running differnt versions of Linux. I presume that when you boot up in Arch Linux it shows the same discrepancy now.

Linux only reads the hw clock at boot or when it decides to sync the hw clock to the time it worked out itself. For these to be 15 minutes apart without being up for months is also rather unlikely.

The most likely cause is that your hw clock is simply wrong. You can set the system clock (then one Linux uses at runtime) using the date command or via ntp. Once this is done, you need to set the hw clock - which is done with the hwclock command.

You'll find descriptions of using the date and hwclock commands in the man pages on your local machine.

The problem may be due to different time assumptions of Linux and MS Windows. By default, MS Windows assumes the time is stored in local time while Linux assumes the time is stored in UTC time. Consequently one of your operating systems will show wrong time when you are dual-booting. The solution might be, either make Linux use local time; or make MS Windows use UTC. The second option is probably not easy and I am not aware how to change these things in that OS. However, if you want to make Linux use local time, you can do that by this command:

timedatectl set-local-rtc 1 --adjust-system-clock

Thereafter if you run the command you have shown us timedatectl you will see a slightly different output: “RTC in local TZ: yes”.

while the other answers do work, it's recommended to Set both Linux and Windows to use UTC, Some versions of Windows revert the hardware clock back to localtime if they are set to synchronize the time online. (Windows by default uses localtime)

It can be done by a simple registry fix: Open regedit and add a DWORD value with hexadecimal value 1 to the registry HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal

You can do this from an Administrator Command Prompt

C:\>reg add "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TimeZoneInformation" /v RealTimeIsUniversal /d 1 /t REG_DWORD /f

Alternatively, create a *.reg file (on the desktop) with the following content and double-click it to import it into registry:

Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation] "RealTimeIsUniversal"=dword:00000001

Should Windows ask to update the clock due to DST changes, let it. It will leave the clock in UTC as expected, only correcting the displayed time.

The Hardware clock and System clock time may need to be updated after setting this value.

If you are having issues with the offset of the time, try reinstalling tzdata and then setting your time zone again

example

timedatectl set-timezone America/Los_Angeles

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