The problem originates from the fact that seemingly, the following code does not return an object:

my $at = localtime $sb->atime;
[download]

You could print out the result of $sb->atime, or look into the documentation of the module to find out how it behaves on your Windows 2000 desktop.

As you are using $at as an object later on, you want to synthetize an object for the "unknown" value as well. As I don't know what kind of module you are using that overrides localtime, I can't offer much more help here.