Here is his example:

6/13/2005 5:59:57 PM 10.1.1.2 WARNING Jun 13 2005 22:00:04: %PIX-4-106
+023: Deny udp src aliens:192.168.1.35/1148 dst dmz:10.10.10.32/1434 b
+y access-group "aliens"
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He said that he wanted to convert the Jun (in the second timestamp) to 06. Earlier in the log entry, there is another timestamp. The first timestamp appears to be from 5:59 pm, the second around 10:00 pm. You are making the assumption that the two datestrings in the log file are identical and interchangable.

Regex error: "(%PIX+)" this matches what? "%PIX" and then an unlimited number of Xs? You surely mean "(%PIX.+)", since the way you have it deletes everything in his example log entry after the 'X'.