Historical clue formulations

• Cue — 2026-03-29
• Encrypted messaging software — 2025-06-23
• Yawn, for wanting guests to leave — 2022-07-07
• Traffic light — 2022-05-06
• A wink or a nod, maybe — 2015-12-13
• Wink, e.g. — 2011-02-16
• Prepare to turn — 2010-07-28
• Cue — 2007-04-02
• Pair of lamps, maybe — 2004-05-09
• Wave, e.g. — 2004-02-08
• Flag, maybe — 2003-06-13
• Nod, at auctions — 2003-05-28
• A wink or a nod, say — 1998-06-03
• Use a heliograph — 1994-08-11