Posting for future reference - there is an interesting difference between the WMI cmdlets (which behave more like VBScript), and the Get-CimInstance cmdlets.

More legacy PowerShell stuff for future reference:

Might be useful to convert WMI UTC string date format to native VBScript: https://www.informit.com/articles/article.aspx?p=23751&seqNum=3

This Microsoft doc is good for converting CIM_DATE format to VT_DATE (native VBScript date/time format)
https://docs.microsoft.com/en-us/windows/win32/wmisdk/swbemdatetime#examples

However, the note on this SE post indicates that the WbemScripting.SWbemDateTime object is not available on older operating systems:
https://stackoverflow.com/a/29537092/2134110
and I confirmed this in the MSDN 2003 library --- SWbemDateTime was first available in Windows XP and Windows Server 2003. So older OSes won't have it and will instead need to be parsed as mentioned in the informit.com article linked above.

The yyyyMMddHHmmss format comes from the Distributed Management Task Force (DMTF)'s Common Information Model (CIM) specification. See: https://docs.microsoft.com/en-us/windows/win32/wmisdk/date-and-time-format

WMI puts strings in this format to comply with the standard.

However, SMBIOS uses a different standard, also published by the DMTF. The SMBIOS standard says that the release date must be a string in the format "MM/DD/YYYY" or "MM/DD/YY" for a BIOS released 1999 or prior. Source: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.4.0.pdf

How to get BIOS information on Linux:
https://stackoverflow.com/a/20604726/2134110

Also:
https://wiki.ubuntu.com/DellBIOS

Both sources confirmed that SMBIOSBIOSVersion/bios-version and ReleaseDate/bios-release-date are the most important data points. Manufacturer/bios-vendor is also useful.

This post seems to suggest ISO 2601 format for string-based date output: https://stackoverflow.com/a/49562607/2134110

So maybe the move is to convert the DMTF date to ISO 2601 format for string output, and then DMTF to native VBScript/PowerShell datetime format

This SE post is pretty good reference for converting .NET datetime to ISO 2601. https://stackoverflow.com/questions/114983/given-a-datetime-object-how-do-i-get-an-iso-8601-date-in-string-format

This is a useful function to determine whether a given date falls into DST:
https://www.robvanderwoude.com/files/isdst_vbs.txt
It requires Windows NT4 SP4 (or later), Windows 2000, or later

Leaving open until PowerShell code is written