Historical clue formulations

• N.F.L. team that has sold out every home game since 1970 — 2024-04-12
• Winners of Super Bowl 50 — 2021-06-16
• Frat dude + Cpls. and sgts. — 2018-09-05
• Denver gridders — 2006-08-29
• Mile High City team — 2005-04-05
• 1991 American Conference champs — 1994-04-05