In 2007, Nippon Ramen Association was established in Tokyo. Later in 2017, the Association applied to Japan Anniversary Association to set July 11 to be Ramen Day (ラーメンの日).
There are two reasons that Ramen Day is set on July 11. Firstly, the number 7 looks like a spoon (more or less) and 11 a pair of chopsticks, the tableware used in eating ramen. Secondly, July 11 is the birthday of TOKUGAWA Mitsukuni (徳川光圀, 1628.7.11 - 1701.1.14), a lord (of some sort, easily noticeable from the family name TOKUGAWA) during the Edo era. Mitsukuni was the first Japanese to try out many foreign cuisine, e.g., dumplings, cheese, natto, etc. He was once recognized as the first Japanese to ead ramen, but some ancient literature suggested otherwise. Still, Mitsukuni was considerably influential in the popularization of ramen. Thus, the date is set.
Since the establishment of the Ramen Day, on July 11, many ramen restaurants host events to boost consumption of ramen. It also happens on SNS, causing the tag to trend.