I could not find server\lib\logstr_en.txt in our IS installation (perhaps because we installed IS on Unix as opposed to NT). However, I was able to accomplish the same thing by changing the following configuration item in server/config/server.cnf:
old: watt.server.serverLogFmt={4} [{6}{7}.{1}.{0,number,0000}] {3}
new: watt.server.serverLogFmt={5} [{6}{7}.{1}.{0,number,0000}] {3}
Thanks for the tip though because those hex dates were rather annoying 
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