Historical clue formulations

• Tiny fraction of a min. — 2021-04-16
• Time it takes light to travel .3 mm: Abbr. — 2020-10-15
• Tiny fraction of a min. — 2016-08-30
• One 60-trillionth of a min. — 2013-09-29
• Tiny fraction of a min. — 2011-12-07
• Tiny fraction of a min. — 2008-11-28
• Infinitesimal division of a min. — 2004-10-13
• 1/60 of a trillionth of a min. — 2001-06-24
• Time it takes for light to travel .3 mm — 1998-05-22