3 Easy Ways to Find Windows Last Boot Time – A Comprehensive Guide


Knowing when your Windows machine was last booted up can provide valuable insights when troubleshooting performance issues or tracking uptime metrics.

As a fellow tech geek, I often need to check the last boot time on my Windows devices. So in this comprehensive guide, I‘ll share multiple easy methods that you can use to find the last boot time on your system.

I‘ll cover different options using PowerShell, Command Prompt, and Task Manager. I‘ve also included sample outputs and my own tips based on experience to help you get the last boot time quickly.

Let‘s dive in!

Why Check Last Boot Time?

Before we look at the different ways to find the last boot time, you may be wondering – why is this information useful?

Here are some common scenarios where knowing the last boot time can help:

• Troubleshooting system problems: If a Windows computer is behaving erratically, checking the last reboot time can reveal if it was booted recently. Any major issues may correspond to a boot event.

• Tracking uptime: For critical systems like servers, uptime is an important metric. The last boot time helps calculate total uptime.

• Identifying pending updates: If you find that the last reboot was several days ago, pending updates may need to be installed. Windows usually requires a reboot after major updates.

• Correlating events: You can match up the last boot time with other system events like application crashes to identify potential relationships.

• Auditing reboots: Checking the last boot time can reveal unauthorized or unintended reboots of servers or computers.

So in summary, knowing the last boot time provides vital temporal context for diagnosing problems, tracking metrics, and correlating system events.

Using PowerShell to Check Last Boot Time

In my experience, PowerShell provides the most flexible options to retrieve the Windows last boot time. Let‘s go over the different PowerShell commands and techniques.

Get-CimInstance

The Get-CimInstance cmdlet can query the CIM (Common Information Model) repository to fetch the last boot time information.

CIM stores management data about system components in an organized hierarchical structure. Get-CimInstance allows you to tap into this management data from PowerShell.

To get the last boot time using CIM, run:

Get-CimInstance -ClassName Win32_OperatingSystem | Select-Object CSName, LastBootUpTime

This retrieves the LastBootUpTime property from the Win32_OperatingSystem CIM class and displays it neatly along with the computer name.

Here‘s what the output looks like on my PC:

CSName        LastBootUpTime
------        --------------
MyPC          2/5/2023 9:15:30 AM

As you can see, this directly gives me the date and time when my system last booted up. Very handy!

Tip: You can also view additional CIM system properties by omitting the Select-Object filter:

Get-CimInstance -ClassName Win32_OperatingSystem

This will list all available properties including LastBootUpTime.

Get-WmiObject

Similar to Get-CimInstance, the Get-WmiObject cmdlet queries the WMI (Windows Management Instrumentation) repository to return system information.

Use it to fetch last boot time like so:

(Get-WmiObject -Class Win32_OperatingSystem).LastBootUpTime

However, the output is in a numeric format rather than a human-readable date:

20230205091530.500000+060 

This represents:
Year 2023, Month 02, Day 05, Hour 09, Minutes 15, Seconds 30, Milliseconds 500000, GMT/UTC +060.

We can translate it to an actual date by passing the raw value through ConvertToDateTime():

Get-WmiObject Win32_OperatingSystem | Select-Object @{LABEL=‘LastBootUpTime‘;EXPRESSION={$_.ConvertToDateTime($_.LastBootUpTime)}}

Now the output is much more useful:

LastBootUpTime
--------------
2/5/2023 9:15:30 AM

So Get-WmiObject gives you greater control over the boot time format compared to Get-CimInstance.

Get-Uptime

On PowerShell 6 and above, you can use the built-in Get-Uptime cmdlet to get system uptime information.

To directly return just the last boot time using Get-Uptime, run:

Get-Uptime -Since

This will cleanly output the date and time of the last boot without any extra properties.

While Get-Uptime is the simplest option, it‘s only available in PowerShell 6 and higher. The previous CIM and WMI commands work on all PowerShell versions.

Pro Tip: You can call Get-Member on the WMI/CIM objects to view all available properties and methods for retrieving system data:

Get-WmiObject Win32_OperatingSystem | Get-Member

This helps discover other useful information you can query alongside the last boot time.

Checking Last Boot Time via Command Prompt

Apart from PowerShell, you can find the last boot time directly from the good old Command Prompt with some conventional commands.

Let‘s go through them:

systeminfo

The systeminfo utility displays detailed Windows configuration information including last boot time:

systeminfo | find "System Boot Time"

This filters its verbose output to show:

System Boot Time: 2/5/2023, 9:15:30 AM

wmic

The Windows Management Instrumentation Command line tool (wmic) can query WMI repositories from the command line.

Use it to return the last boot time as follows:

wmic os get lastbootuptime

This will output the boot time in the numeric format we saw earlier with PowerShell‘s Get-WmiObject.

net statistics

The net statistics command shows useful network traffic statistics for your system. It also displays uptime information:

net statistics workstation

Look for the "Statistics since" line in the output:

Statistics since 2/5/2023 9:15:30 AM

This tells you when the system was last restarted.

While these Command Prompt utilities get the job done, I prefer the greater flexibility of PowerShell for accurately retrieving the last boot time.

Viewing Last Boot Time in Task Manager

You can also conveniently check system uptime since the last boot using the Task Manager in Windows:

• Launch Task Manager with Ctrl + Shift + Esc
• Switch to the Performance tab
• Look for the Uptime field at the bottom

For example, my Task Manager currently shows:

Up Time: 2 days 5 hours 31 minutes

This lets me quickly see how long the system has been running since the last boot, rather than the actual boot time.

Task Manager provides a fast graphical way to glance at uptime. But for the precise last boot time, PowerShell or the command line utilities are better suited.

Why Is Getting the Accurate Boot Time Important?

You may be wondering, why go through the hassle of getting the exact last boot time rather than just the uptime?

Here are some reasons why the specific boot time matters:

• It allows you to correlate the boot event with timeline of other system activities like application logs, shutdown events etc.

• You can use it to calculate metrics like average time between reboots, frequency of restarts etc.

• It serves as an audit trail to analyze unauthorized or irregular reboots.

• You may need to determine if reboot occurred before or after a particular activity.

• It helps identify patterns like recurring crashes or hangs that require restarts.

• You can use it to check if reboot was performed during specific maintenance window.

In summary, while uptime gives a general sense of availability, the precise boot time provides vital temporal context for diagnosing problems and analyzing system behavior.

As an admin, I always try to log and monitor boot times along with uptime for a complete picture.

Factors That Could Alter Last Boot Time

Now that you know how to get the Windows last boot time, it‘s also important to be aware of certain factors that can modify or reset this value:

• Daylight savings time change: The boot time will shift by an hour with the DST switchover.

• Time sync issues: If system time is not syncing properly with a time server, the last boot time will be incorrect.

• Dual booting: Multi-boot systems may show the last boot time of other OS instead of Windows.

• Sleep and hibernate: Entering sleep or hibernate will reset the boot time to the wake time.

• Virtual machines: The boot time inside VMs can differ from the host machine‘s time.

• Time tampering: Modifying the system time manually or via malware will invalidate the last boot time.

So you need to account for these factors when analyzing the boot time data. Cross-verifying with logs from BIOS, UEFI or a time server can help overcome potential timing discrepancies.

Bonus: Calculate Uptime from Last Boot Time

Once you have the last boot time of your Windows system, you can easily calculate the uptime like so:

$LastBootTime = Get-CimInstance -ClassName Win32_OperatingSystem | Select-Object LastBootUpTime

$Uptime = (Get-Date) - $LastBootTime.LastBootUpTime 

Write-Output "System Uptime: $Uptime" 

This will output the system‘s uptime since the last restart, similar to Task Manager.

Knowing both the precise boot time and overall uptime gives you comprehensive visibility into your system‘s availability.

Closing Thoughts on Finding Windows Boot Time

I hope this guide has helped you learn multiple handy methods to find the last boot time in Windows.

To recap, PowerShell cmdlets like Get-CimInstance provide flexible options to retrieve the boot time, while Task Manager shows a quick uptime overview.

But the actual utility depends on your specific requirements – whether you need boot time auditing, diagnosing issues, calculating uptime and so on.

Try out these techniques yourself and let me know which one works best for you! I‘m always looking to learn new tricks from fellow Windows users and tech enthusiasts.