The WMI cmdlets do not convert date-time properties found in WMI. Querying the Win32_Process class for the creation date of a process returns the date-time property as a long string:

PS> Get-WmiObject Win32_Process -Filter "ProcessId=$PID" | Select Name, CreationDate
Name               CreationDate            
----               ------------            
powershell_ise.exe 20170209120229.941677+000

The .NET namespace used by the WMI cmdlet, System.Management, includes a class called ManagementDateTimeConverter, dedicated to converting date and time formats found in WMI.

The string in the preceding example may be converted as follows:

Get-WmiObject Win32_Process -Filter "ProcessId=$PID" | 
    Select Name, @{Name='CreationDate'; Expression={ [System.Management.ManagementDateTimeConverter]::ToDateTime($_.CreationDate) }}