#!/usr/bin/perl -n
next if /.../;
s/.../.../;
s/.../.../;
if( /.../ ) {
    my( $date, $time )= /(\d([-/\d]+\d) (\d([\d:.]+\d)/;
    my( $hr, $min, $sec, $ms )= split /[:.]/, $time;
    my $now= $ms/1000 + $sec + 60*( $min + 60*$hr );
    if(  $Then  ) {
        $sec= $now - $Then;
        $min= int( $sec / 60 );
        $sec -= 60*$min;
        $_= sprintf "+%d:%06.3f %s", $min, $sec, $_;
    }
    $Then= $now;
}
print;
__END__
...