Historical clue formulations

• Geological period — 2026-09-19
• Geological time unit — 2024-03-18
• It's quite the stretch — 2023-02-05
• Early Jurassic, e.g. — 2022-09-21
• Period of history — 2021-06-27
• Anthropocene, for one — 2021-06-04
• Pliocene, e.g. — 2020-12-13
• Long time — 2020-04-22
• The Oligocene, e.g., in geology — 2019-09-29
• Memorable time — 2018-12-28
• Historical stretch — 2018-05-23
• Notable time period — 2017-01-10
• Late Jurassic, e.g. — 2016-09-10
• Many, many years — 2015-08-10
• Historic time — 2015-01-11
• Historical period — 2014-12-15
• Timeline segment — 2014-04-18
• Geologic span — 2013-02-27
• Several ages, in geology — 2013-01-21
• Notable time span — 2012-11-29
• Period in history — 2012-02-14
• Memorable time — 2011-04-10
• Eocene, e.g. — 2010-07-01
• Pleistocene, e.g. — 2009-04-15
• Ages and ages — 2009-04-12
• Part of a period, geologically — 2008-06-11
• Geologic time unit — 2008-03-10
• Geologic period — 2007-05-30
• Period — 2006-06-18
• Long, long time — 2006-04-04
• Time — 2005-08-28
• Geologic period — 2004-02-17
• Notable period — 2003-04-28
• Period — 2003-03-15
• Long time — 2003-01-11
• Historical period — 2001-10-24
• Period in history — 2001-04-24
• Notable period — 2000-10-23
• Memorable time — 2000-09-18
• Age — 2000-07-26
• Notable period — 1999-09-27
• Historic time — 1999-07-29
• Significant time — 1997-08-13
• Part of a period — 1997-05-03
• Geologic time — 1995-07-31
• Long time — 1995-04-20
• Time to remember — 1994-11-11
• Eocene, for one — 1994-09-30