Windows defaults to setting the (RTC) real-time-clock to local-time and Linux sets RTC in UTC (universal-time).
This makes your time/timezone floating in space where it may be in doubt what time it actually is.
The best approach to keep both working is to set your RTC (hardware clock) to UTC
# timedatectl set-local-rtc 0
# hwclock --systohc --utc
And enable a network-time-daemon on Linux.
# systemctl enable --now systemd-timesyncd
Ensure your timezone is correct linking it to your
/etc/localtime e.g for Jerusalem (Replace in the command below Continent/City case sensitive location)
# ln -sf /usr/share/zoneinfo/**Asia**/**Jerusalem** /etc/localtime
The get a list of supported zone groups (Continent)
find /usr/share/zoneinfo/ -maxdepth 1 -type d
Then list the content of your selected zone e.g. Asia (Cities)
Next step is to boot into Windows and instruct Windows to handle the hardware clock in UTC.
This is done by adding an entry to the system registry. To avoid messing with the Registry Editor (regedit.exe) creating a file to import is the safest method.
Create a file on your Windows system using Notepad (notepad.exe) and name it
utc.txt and save it on your desktop.
Rightclick your desktop → New → Text document
Copy/Paste below content as you need absolutely no errors.
Depending on your version of Windows this may work.
Older versions of Windows may import the file without complaints
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation] "RealTimeIsUniversal"=dword:00000001 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient] "Enabled"=dword:00000000
Newer versions presumably Windows 10 requires the registry editor version and an empty line
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation] "RealTimeIsUniversal"=dword:00000001 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient] "Enabled"=dword:00000000
When you have saved the file, open a command prompt and navigate to your Desktop folder and rename the file to
C:\Users\username> cd Desktop
C:\Users\username\Desktop> move utc.txt utc.reg
When you have renamed the file it can be imported into the registry by double clicking the .reg file found on your desktop.
Accept the disclaimer to import the keys and reboot your system.
Besides letting Windows use the systems RTC the registry keys also disables the Windows NTP client - so only Manjaro will adjust your clock.