For those who don’t know what a lucky bag is , here is the description i ganked from wikipedia
Fukubukuro (福袋 lucky bag, mystery bag) is a Japanese New Year’s Day custom where merchants make grab bags filled with unknown random contents and sell them for a substantial discount, usually 50% or more off the list price of the items contained within. The low prices are usually done to attract customers to shop at that store during the new year. The term is formed from Japanese fuku (福, good fortune/luck) and fukuro (袋, bag).
As described, they are usually sold on the 1st january but some are sold prior. And sometimes you also get to know what is in each of them. I have complied a small list of the ones i have seen so far.