You are still right... With my solution, if I change the default  portal language after some image has been already added into a gallery and then I try to add another one, I recive an exception.
However, although I think that is unusually  to change the default portal language, an alternative should be to use the Services.Localization.Localization.SystemLocale that is a constant  (Public Const SystemLocale As String = "en-US"),
so all dates will be written and read in the same format, and finally, will be displayed to each user  in his prefered format.

Here how I Would do...

In Components/Utilities/XML.vb

At the top of the page i would insert

Imports System.Threading

Imports System.Globalization

Then I would create a new sub

Private Sub SetCurrentThreadCulure()

Dim ci As CultureInfo

ci = New CultureInfo(Convert.ToString(Services.Localization.Localization.SystemLocale))

Thread.CurrentThread.CurrentCulture = ci

End Sub

Finally i Would call the above sub where is needful

In

Public Shared Sub SaveMetaData - ( at the begin),

Public Function CreatedDate - ( at the begin) and

Public Function ApprovedDate - ( at the begin).

No date.ParseExact is needful, only DateTime.Parse(iterator.Current.Value()) or simply CDate(iterator.Current.Value())

I belive this should work. Bye