How to parse this timestamp?

[gnu.gcc.help]

I've got timestamps in a file that look like:

[19-Aug-2007 07:38:43+216ms NZST]

How can I parse them?  I don't see any way to build a strftime()
format string that can handle the +216ms part. The best I can see is
tearing it all apart with a regex, but I'm trying to avoid that pain
if I can.

(PS: I have no clue why google groups thinks it should put
"gnu.gcc.help" on the from line)