Time Issue in Windows and Linux

One of the most common and annoying problems when using Windows and Linux on the same computer is constant system time desynchronization.

Why does this happen?

The problem arises from different approaches to storing time in BIOS/UEFI:

• Linux assumes that BIOS stores time in UTC (Coordinated Universal Time) format
• Windows assumes that BIOS stores time in local timezone

When you switch between systems, each of them adjusts the BIOS time in its own way, leading to constant desynchronization.

Understanding the Problem

How Time Works in Linux

Linux uses UTC as hardware time by default:

1. System reads time from BIOS as UTC
2. Applies timezone offset
3. Displays local time to user

Example: If BIOS has 12:00 UTC and you’re in UTC+3 timezone, Linux will show 15:00.

How Time Works in Windows

Windows uses local time directly:

1. System reads time from BIOS as local
2. Displays it without conversions
3. When changing time, writes local time back to BIOS

Example: If BIOS has 15:00, Windows will show 15:00 (without timezone consideration).

What Happens When Switching

1. Boot into Linux → Linux reads time as UTC and adds offset
2. Reboot into Windows → Windows reads the same time as local
3. Result: Time in Windows is off by your timezone amount!

Solution

There are two approaches to solving this:

1. Configure Linux to use local time (not recommended)
2. Configure Windows to use UTC

We’ll use the second approach as it’s more technically correct.

Step 1: Determine System Architecture

Before executing the command, you need to determine whether you have a 32-bit or 64-bit version of Windows.

How to check architecture:

1. Press Win + Pause/Break
2. Or: Settings → System → About
3. Find the “System type” line

Most likely, you have a 64-bit system (this is standard for modern computers).

Step 2: Execute Registry Configuration Command

1. Open Command Prompt as administrator

2. Depending on your system architecture, execute the corresponding command

For 64-bit systems (most common):

Reg add HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation /v RealTimeIsUniversal /t REG_QWORD /d 1

For 32-bit systems (rarely encountered):

Reg add HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation /v RealTimeIsUniversal /t REG_DWORD /d 1

What does this command do?

The command adds the RealTimeIsUniversal parameter to the Windows registry with value 1, which tells the system to interpret hardware time as UTC rather than local time.

After executing the command, you should see the message:

The operation completed successfully.

Step 4: Disable Time Synchronization Service

To prevent Windows from trying to “fix” the time back, you need to disable the automatic synchronization service:

sc config w32time start= disabled

Important!

Note the space after start= — this is not a typo! The command should be exactly like this: start= disabled (with a space).

After execution, you’ll see:

[SC] ChangeServiceConfig SUCCESS

Result

After completing all steps:

• Time in Windows is always correct
• Time in Linux is always correct
• No need to manually adjust the clock
• Problem solved forever

Reverting Changes

If for some reason you need to revert everything back:

Remove registry parameter:

Reg delete HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation /v RealTimeIsUniversal /f

Enable synchronization service:

sc config w32time start= auto

After this, restart your computer.