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Windows PowerShell, 81
Since I did not create an implementation when writing the task I feel myself eligible to golf it from the start, too :-)
-join" .':
"[(($d="$(date)$args"[-8..-1]-ne58)|%{($_-band12)/4})+,4+($d|%{$_%4})]
History:
2011-02-26 23:50 (119) First attempt.
2011-02-26 23:55 (...