Historical clue formulations

• Heavens — 2026-07-16
• Heavens — 2026-07-08
• Old-time anesthetic — 2025-11-10
• Thin air — 2025-10-28
• Number discovered in the 1500s — 2025-10-24
• Anesthetic first used on a patient in 1842 — 2025-09-07
• Heavens — 2025-07-07
• Upper atmosphere — 2024-12-25
• Early number? — 2024-02-23
• Heavens — 2023-03-31
• Anesthetic since the 1840s — 2022-12-15
• Upper atmosphere — 2022-04-01
• Air up there — 2022-03-17
• Onetime dentist's supply — 2022-02-27
• Heavens — 2021-12-18
• Clear sky — 2021-04-17
• Upper atmosphere, with "the" — 2021-04-08
• Fifth element, to Aristotle — 2021-03-26
• Thin air — 2021-01-13
• Anesthetic of old — 2020-08-30
• Old anesthetic — 2020-08-11
• It's a knockout — 2020-04-22
• Old knockout? — 2020-03-06
• Old anesthetic — 2019-11-11
• Old anesthetic — 2019-10-14
• Old dentist's supply — 2019-07-14
• What radio signals travel through, with "the" — 2019-06-30
• Antiquated anesthetic — 2018-08-05
• Bygone anesthetic — 2018-07-04
• Anesthetic of old — 2018-04-08
• Heavens, poetically — 2017-09-18
• It'll knock you out — 2017-06-11
• Early anesthetic — 2017-05-23
• Anesthetic of old — 2017-01-18
• Surgeon's supply in the old days — 2016-11-08
• Thin air — 2016-06-30
• Upper reaches — 2016-04-17
• Early anesthetic — 2016-03-02
• Upper reaches of space — 2016-02-24
• Old anesthetic — 2016-01-13
• It's a knockout — 2015-09-18
• Lead-in to net — 2015-04-14
• Clear sky — 2014-07-13
• C4H10O — 2014-06-29
• Upper regions of space — 2014-03-28
• It's a knockout — 2014-01-05
• Dr. Larch's drug in "The Cider House Rules" — 2013-09-11
• Dioxane, e.g. — 2013-01-19
• Knockout number? — 2012-10-18
• Aristotle's "fifth element" — 2012-07-29