What's the biggest online shopping day in the world? Not Valentine's Day. Not Cyber Monday or Black Friday. The winner is China's Singles' Day, celebrated on November11, or 11.11.

    Singles' Day began as a day for unmarried or uncoupled people to celebrate their lives. Single students, looking for an excuse to buy themselves presents, started it on November11,1993, reported The Guardian. It is symbolized by the four mumber ones in the date of November11 and is also called Double Eleven, in reference to the day it was started, said the BBC. It became a major shopping day in 2009. The CEO of an online shopping site --Alibaba-- tried to increase sales at the e-commerce company. The CEO, Daniel Zhang, launched an annual online sale on that day, said Fortune. When it first began, "Sigles' Day was very much an offline comfort to actual single people," noted the website atlas Obscura."A small group of students at Nanjing University are said to have chosen 11.11 as a day that singles could do activities like karaoke together." It quickly became a cultural phenomenon.

    Last year, Alibaba sold more than $1 billion worth of products in the first three minutes of the sales, reported Bloomberg News. Total sales on Singles' Day soared to $9 billion within 24 hours. That's four times bigger than Cyber Monday in the U.S., which is the Monday after Thanksgiving and traditionally a big shopping day. By comparison, online sales in the U.S. last year on Black Friday were just $1.5 billion, reported TechCrunch.

    Today, Singles' Day is very successful. Analysts say that this year, sales on China's Singles' Day will increase to a new high. In the U.S., Jennifer Wang, a co-founder of a company targeting Chinese-Americans, said, "We expect to have 3 million people coming to click Dealmoon for the Singles' Day launch." Some observers think Singles' Day could catch on globally.