Extracting Windows Installation Date

by Jan 31, 2019

Ever wondered how old your Windows installation is? A one-liner can tell:

PS> (Get-CimInstance -Class Win32_OperatingSystem).InstallDate

Freitag, 8. Juni 2018 18:24:46  

Two things are noteworthy: first, we are apparently using a German system. Second, the install date may be much more recent than you think: every new major Windows 10 update actually performs a full reinstall.

If you’d like to change the culture for a DateTime output, simply use ToString() and a CultureInfo object:

PS> (Get-CimInstance -Class Win32_OperatingSystem).InstallDate.ToString([System.Globalization.CultureInfo]'en-us')
6/8/2018 6:24:46 PM


And if you’d like to know just how old your Windows installation is in days, use New-TimeSpan:

PS> New-TimeSpan -Start (Get-CimInstance -Class Win32_OperatingSystem).InstallDate

Days              : 204
Hours             : 18
Minutes           : 53
Seconds           : 52
Milliseconds      : 313
Ticks             : 176936323133869
TotalDays         : 204,787411034571
TotalHours        : 4914,89786482969
TotalMinutes      : 294893,871889782
TotalSeconds      : 17693632,3133869
TotalMilliseconds : 17693632313,3869

PS> (New-TimeSpan -Start (Get-CimInstance -Class Win32_OperatingSystem).InstallDate).TotalDays

PS> (New-TimeSpan -Start (Get-CimInstance -Class Win32_OperatingSystem).InstallDate).Days

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