Enjoy watching the Earl Thomas Conley "Once In a Blue Moon" music video and see the song details here. . . The Earl Thomas Conley Once In a Blue Moon song was released in January 1986 as the second and final single from his Greatest Hits compilation album. This song was Conley’s eleventh number one on the country chart. The single went to number one for one week starting May 3, 1986 and spent fourteen weeks on the country chart.