Christmas Without KFC? For Many Japanese, That’s Unthinkable

People Celebrate Christmas In Tokyo
A man in Tokyo buying KFC for his family, Dec. 24, 2015 in Tokyo, Japan. A KFC dinner is one of the popular ways to spend Christmas in Japan.
Taro Karibe—Getty Images

From ham and turkey to shortbread and mince pie, people in different parts of the world mark Christmas with all sorts of festive foods. In Japan, that honor falls to buckets of finger-licking’ good chicken from KFC.

About 3.6 million Japanese families mark every Dec. 25 with fried chicken from the outlet owned by Yum Brands (YUM), reports the BBC, and daily turnover at some branches can even shoot up to tenfold the usual during the month of December. The special Christmas menu, known as Christmas Party Barrels, is so popular that some people reserve them weeks before the festive date rolls around. KFC also conducts early-bird promotion campaigns for Christmas orders.

This particular take on Christmas in Japan, a country where not even 1% of the population self-identify as Christians, was reportedly the result of an advertisement campaign waged over 40 years ago by the fried chicken chain.

A KFC Japan spokesperson told the BBC that it all started as an idea for a “party barrel” Christmas special, conceptualized by the manager of the fried chicken store’s first Japanese outlet in 1970, and brought to nationwide popularity in 1974 with an advertisement campaign, “Kentucky for Christmas.”

The fried chicken “filled a void” of Christmas traditions in Japan, Joonas Rokka, a French marketing professor who studied the promotion push, told the BBC. Ever since the ’70s, having KFC for Christmas has endured in Japanese popular culture, and Colonel Sanders, the chain’s mascot, is dressed up for the holiday season, the BBC notes.

For more on fast food, watch Fortune’s video:

In recent years, KFC‘s parent company Yum Brands has been cashing in on the appetite for fast food across Asia — despite slowing sales in in China, which it says are politically linked. Menu items are also known to take new, unexpected twists in this part of the world. For example, “Chizza“—essentially a pizza with a slab of fried chicken in place of dough—first debuted in the chain’s Philippine branches, and was introduced to the Japanese market earlier in October.

Subscribe to Well Adjusted, our newsletter full of simple strategies to work smarter and live better, from the Fortune Well team. Sign up today.