"System.DateTime". Error: "String was not recognized as a valid DateTime."

Hi, Everone

Try http://gallery.technet.microsoft.com/scriptcenter/bb94b422-eb9e-4c53-a454-f7da6ddfb5d6

but 

[PS] F:\MSG>.\1.ps1
Cannot convert value "27.08.2014" to type "System.DateTime". Error: "String was not recognized as a valid DateTime."
At F:\MSG\1.ps1:9 char:36
+ $outfile_date = ([datetime]$rundate <<<< ).tostring("MM/dd/yyyy")
    + CategoryInfo          : NotSpecified: (:) [], RuntimeException
    + FullyQualifiedErrorId : RuntimeException


Started processing XXXXX
Cannot process argument transformation on parameter 'Start'. Cannot convert value "27.08.2014" to type "System.DateTime
". Error: "String was not recognized as a valid DateTime."
    + CategoryInfo          : InvalidData: (:) [Get-MessageTrackingLog], ParameterBindin...mationException
    + FullyQualifiedErrorId : ParameterArgumentTransformationError,Get-MessageTrackingLog

Processed 0 log records in 0.0439936 seconds
   Average rate: 0 log recs/sec.

Run time was 1.138802 seconds.
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