Historical clue formulations

• King in Norway's Fairhair dynasty — 2025-05-13
• 10th-century European king — 2013-03-23
• 11th-century king of Denmark — 2012-12-02
• Viking king, 995-1000 — 2011-10-13
• King surnamed Tryggvason — 2011-08-05
• Norwegian king until A.D. 1000 — 2011-01-04
• Norwegian king who converted the Vikings to Christianity — 2008-07-24
• Norwegian king of A.D. 1000 — 2007-03-29