xArchive: Get-ArchiveEntryLastWriteTime Does Not Return [DateTime] returns generalized String

[PlagueHO]

Details of the scenario you tried and the problem that is occurring

The Get-ArchiveEntryLastWriteTime function in xArchive should return a [system.datetime] (and the output type report that), but instead it generalizes it to a string.

This causes all sorts of date translation issues on machines with non-US date formats. Including test failures and other very difficult to diagnose issues.

We should avoid converting date/times to/from string when we need to compare them.

I'll be fixing this in a PR shortly (once I can get all the other broken archive tests sorted).

Verbose logs showing the problem

https://github.com/PowerShell/xPSDesiredStateConfiguration/blob/dev/DSCResources/MSFT_xArchive/MSFT_xArchive.psm1#L992

Suggested solution to the issue

Correct 'Get-ArchiveEntryLastWriteTime' to return [datetime]

The DSC configuration that is used to reproduce the issue (as detailed as possible)

N/A

The operating system the target node is running

OsName               : Microsoft Windows 10 Enterprise
OsOperatingSystemSKU : EnterpriseEdition
OsArchitecture       : 64-bit
WindowsVersion       : 1803
WindowsBuildLabEx    : 17134.1.amd64fre.rs4_release.180410-1804
OsLanguage           : en-US
OsMuiLanguages       : {en-US}

Version and build of PowerShell the target node is running

Name                           Value
----                           -----
PSVersion                      5.1.17134.407
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.17134.407
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

Version of the DSC module that was used ('dev' if using current dev branch)

dev

I expect this is the same in PSDscResources - so I'll raise and fix over there too.