"Lucky 13" is really contradictory, used most often as a joke. This is because 13 is generally revered as an unlucky, or evil number. There is also some significance between the 13th of the month landing on a Friday, as "Friday the 13th" is usually viewed as an unlucky day. Lucky 13 is usually used as a joke as it is contradictory to what you would normally expect. Please allow up to 3 weeks for delivery.