| "Good Day" | ||||
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&sq=&lang=&file=File:IU,_Good_Day_(JPN_Version;_CD_Cover).png) Regular and digital edition Japanese single cover | ||||
| Single by IU | ||||
| from the album Real and Good Day | ||||
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| Released | December 9, 2010 | |||
| Length | 3:53 | |||
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| IU singles chronology | ||||
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| IU Japanese singles chronology | ||||
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| "Good Day" on YouTube | ||||
"Good Day" (Korean: 좋은 날; RR: joheun nal) is a song recorded in two languages (Korean and Japanese) by South Korean singer IU. The Korean version was released on December 9, 2010, as the lead single for IU's third extended play (EP) Real. It was written by Kim Eana, while production was handled by Lee Min-soo. The Japanese version was originally included on IU's first Japanese extended play I□U, released on December 14, 2011, before being released on March 21, 2012, as IU's first single album Good Day.
"Good Day" received generally positive reviews by music critics. Billboard magazine crowned it as the best K-pop song released in the 2010s. Commercially, the song debuted atop the Gaon Digital Chart, topping the chart for five weeks and becoming the sixth best-selling single in South Korea, selling more than 4.4 million digital units. The Japanese version reached the top five on the Oricon Singles Chart, and sold more than 30,000 physical copies in the country.