America’s national days of shopping, Black Friday and Cyber Monday, continue to increase their global footprints. In China, sales during Amazon.com Inc.’s two-day “Black Friday” event were 400% more than on China’s big Singles’ Day sale Nov. 11.

In addition to hopping on the Black Friday/Cyber Monday bandwagon, shoppers also are following U.S. consumers in the shift to shopping on mobile devices. Comparing 2014 to 2013, consumers in the United Kingdom spent 414% more in mobile apps on iPhones and 306% more in mobile apps on Android smartphones on Black Friday, Nov. 28, according to data from mobile retail technology vendor NN4M.

That comes at the same time as sales via mobile apps on Cyber Monday, Dec. 1, across both mobile platforms decreased compared to last year. NN4M did not release specific sales figures.

That decrease shows that Black Friday has overtaken Cyber Monday in the U.K as the top day for e-commerce sales, NN4M says. “We’re excited to see a dramatic increase in native mobile app usage across the board through this crucial shopping period,” says Lorraine Howard, director of NN4M.

NN4M clients include some of the U.K.’s largest retailers: apparel retailer River Island Clothing Co. Ltd., retail chain Debenhams Plc., upscale department store House of Fraser Stores Ltd. and Mothercare Ltd., which sells items for expectant mothers. River Island is No. 174 in the2014 Internet Retailer Europe 500 (Learn about the top players in e-commerce in Europe https://www.internetretailer.com/europe500/), Debenhams No. 46, House of Fraser No. 98 and Mothercare No. 126.

Motherview views its apps and mobile sites as equally important, though serve different audiences, says Chris Bertin, group mobile commerce manager. “We see that customers who use apps are more loyal, spend more per transaction and convert better,” he says. “Whereas our mobile site is used more for research and to locate our stores, therefore we see slightly lower conversion and higher traffic.”

One of NN4M’s apps is downloaded every nine seconds, the company says, and it sends more than 20 million push notifications every month. A push notification is a message that appears on a mobile device screen and sounds an alert whether a consumer has the related app open or not, or whether a mobile device is on or asleep. Push notifications can alert a shopper to a sale or pop up when a shopper is close to a physical store.