Converting Those Weird WMI Dates and Times

Today's post is a follow-along. Fire up a copy of PowerShell (even v1 will do) and try this:

Get-WmiObject -class Win32_OperatingSystem | Select-Object LastBootUpTime

What the heck is that date and time all about? The problem with most WMI classes is that they store dates and times in a fairly hard-to-read form. Fortunately, PowerShell dynamically adds a couple of methods to ALL WMI classes, enabling you to convert between "Weird WMI Time" and "Normal Time." Here's an example:

Get-WmiObject -class Win32_OperatingSystem | Select-Object __SERVER,@{label='LastRestart';expression={$_.ConvertToDateTime($_.LastBootUpTime)}}

This makes use of the current WMI object's ConvertToDateTime() method, and asks it to convert the current object's LastBootUpTime property. This can be done with pretty much any WMI date and time, and it also demonstrates the trick of using a hashtable to create custom columns in your output. Do pay close attention to those (parentheses) and {curly braces}, as PowerShell is pickier than a fourth-grade English teacher when it comes to punctuation.

A closing thought: The above hashtable trick with the custom output column also works with the Format-Table cmdlet. In v1 of PowerShell, Select-Object and Format-Table used a slightly different syntax to create custom properties/columns; in v2, Microsoft changed things so that both commands use either set of syntax. This is a really great technique to have in your utility belt, since it's got a ton of useful applications. 

Where might you use this trick? What WMI date and time properties do you find yourself dealing with?