SEOUL (REUTERS) - Many South Koreans marked "Black Day" on Friday (April 14), but it had nothing to do with concerns that North Korea may conduct a weapons test, or that the United States, the South's main ally, may launch a pre-emptive strike to stop it.

It had nothing to do with Good Friday or Black Friday either.

"Black Day" in South Korea is a day for singles, marked by eating "jajangmyeon", a noodle dish topped with a thick sauce made of black beans.

It's celebrated by singles as a response to"White Day", an Asian Valentine's Day which falls a month earlier, on March 14.

As tensions grew to a fever pitch elsewhere over the likelihood of North Korea conducting a nuclear or long-range missile test, possibly this weekend, there was little sign of concern in South Korea's capital, Seoul, which lies within range of the North's artillery.

"Outside South Korea, some people are worried, but we don't feel like that in our daily lives," said Choi Na Young, an office worker in central Seoul.

"All I can do is just try my best and work hard," said Choi, as she queued for noodles with colleagues. "So no matter what the outside world thinks, I came here to enjoy Black Day".

"Black Day" was trending on Twitter and was the leading news item on the Naver web portal in South Korea, which has one of the world's highest percentage of Internet users as a percentage of population.

The nonchalance about the possibility of conflict with the North has grown in recent years in the South, which remains technically in a state of war with its neighbour. The 1950-53 war between the two ended in an armistice, and no peace treaty was signed.

In 1994, when North Korea's founding president Kim Il Sung died, there was panic in South Korea that conflict could be just around the corner.

And when North Korea shelled the South Korean border island of Yeonpyeong in 2010, some South Koreans stocked up on dried food and canned goods, fearing the skirmish could escalate into a full-blown war.

Over time, however, sentiment has changed and South Koreans, especially young people, have become used to the bellicose rhetoric and nuclear bluster in the region.

Retailers in Seoul said there was no indication that people were hoarding food or goods in preparation for a conflict."There is no panic buying. None at all," said a spokesman at the Lotte Mart supermarket.

After North Korea's third nuclear test in 2013, the most talked-about term on South Korean web portals and social media networks was "Innisfree", a popular cosmetics brand which had just announced big discounts.

"Usually, the further one is from Korea, the more one expects there to be war," said Andrei Lankov, a North Korea expert at Seoul's Kookmin University.