Historical clue formulations

• Colorado summer hrs. — 2025-05-21
• Spring hrs. in Colorado Springs — 2020-10-04
• Summer hrs. in Colorado — 2020-07-19
• Colorado summer hrs. — 2019-07-08
• Santa Fe summer hrs. — 2017-04-16
• Summer hours in Denver: Abbr. — 2017-02-06
• Summer hrs. in Colorado — 2016-09-19
• Summer hrs. in Denver — 2012-10-07
• Wyo. is on it in the summer — 2008-12-26
• Denver summer hrs. — 2004-10-17
• Summer clock setting, in the Rockies: Abbr. — 1999-11-19
• Denver summer time: Abbr. — 1994-03-08