localtime() can be used with arguments. When all that you want is the time from 1 hour ago, localtime(time - 3600) should work just fine.

Assuming that your code is working, you could try the following:

use POSIX 'strftime';
$now     = lc strftime("%d/%m/%y %H:%M:%S", localtime);
$hourago = lc strftime("%d/%m/%y %H:%M:%S", localtime(time - 3600) );
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Regards,
Luke