Background: Glenn Lee Beck (born February 10, 1964) is an American talk show host, political commentator, and producer. He is the CEO, founder, and owner of Mercury Radio Arts, the parent company of his television and radio network TheBlaze. A conservative, he hosts the Glenn Beck Radio Program, a popular talk-radio show nationally syndicated on Premiere Radio Networks. Beck also hosts the Glenn Beck television program, which ran from January 2006 to October 2008 on HLN, from January 2009 to June 2011 on the Fox News Channel and currently airs on TheBlaze.
Context: Glenn Lee Beck was born in Everett, Washington, the son of Mary Clara (nee Janssen) and William Beck, who lived in Mountlake Terrace, Washington, at the time of their son's birth. The family later moved to Mount Vernon, Washington, where they owned and operated City Bakery in the downtown area. He is descended from German immigrants who came to the United States in the 19th century. Beck was raised as a Roman Catholic and attended Immaculate Conception Catholic School in Mount Vernon.  Glenn and his older sister moved with their mother to Sumner, Washington, attending a Jesuit school in Puyallup. On May 15, 1979, while out on a small boat with a male companion, Beck's mother drowned just west of Tacoma, Washington, in Puget Sound. The man who had taken her out in the boat also drowned. A Tacoma police report stated that Mary Beck "appeared to be a classic drowning victim", but a Coast Guard investigator speculated that she could have intentionally jumped overboard. Beck has described his mother's death as a suicide in interviews during television and radio broadcasts.  After their mother's death, Beck and his older sister moved to their father's home in Bellingham, Washington, where Beck graduated from Sehome High School in June 1982. Beck also regularly vacationed with his maternal grandparents, Ed and Clara Janssen, in Iowa. In the aftermath of his mother's death and subsequent suicide of his stepbrother, Beck has said he used "Dr. Jack Daniel's" to cope. At 18, following his high school graduation, Beck relocated to Provo, Utah, and worked at radio station KAYK. Feeling he "didn't fit in", Beck left Utah after six months, taking a job at Washington, D.C.'s WPGC in February 1983.
Question: When did Glenn Beck's mother die?

Answer:
On May 15, 1979,