Historical clue formulations

• Periods in the N.B.A.: Abbr. — 2021-09-28
• N.F.L. divs. — 2013-03-20
• N.F.L. periods: Abbr. — 2008-05-06
• N.F.L. game divs. — 2008-04-02
• Game periods: Abbr. — 2006-05-05
• Game divs. — 2005-11-13
• Bowl parts: Abbr. — 2005-11-06