perl -pi.bak -e 's!,(\d+)/(\d+)/(\d+)\s+(\d+):(\d+),!sprintf ",%04d-%02d-%02d %02d:%02d:%02d,", $3,$1,$2,$4,$5,0!ge' csv.txt

# example
while(<DATA>) {
s!,(\d+)/(\d+)/(\d+)\s+(\d+):(\d+),!sprintf ",%04d-%02d-%02d %02d:%02d:%02d,", $3,$1,$2,$4,$5,0!ge;
print
}
__DATA__
blah,11/22/2003 24:07,blah
blah,1/2/2003 24:07,blah

__END__
# produces
blah,2003-11-22 24:07:00,blah
blah,2003-01-02 24:07:00,blah