Historical clue formulations

• Mo. parts — 2026-07-01
• Calendar units: Abbr. — 2021-12-30
• Calendar units: Abbr. — 2019-06-17
• Work cycles: Abbr. — 2007-01-11
• Divs. of a year — 2006-07-10
• Work units: Abbr. — 2004-05-16
• Days on end: Abbr. — 2003-06-14
• Divs. of months — 1998-06-01
• Mo. parts — 1997-12-28
• Cal. units — 1997-06-12