Historical clue formulations

• Clock-setting std. — 2026-07-16
• Prime meridian hrs. — 2025-11-25
• Clock standard: Abbr. — 2025-06-20
• Clock-setting standard: Abbr. — 2024-07-10
• Big Ben hrs. — 2023-02-19
• Intl. standard used by many astrologers — 2022-03-30
• Hrs. at the prime meridian — 2021-07-06
• Setting at the prime meridian, for short — 2020-08-10
• Clock-setting std. — 2017-04-24
• Chronometric std. — 2016-07-21
• BBC World Service std. — 2014-09-06
• Clock-setting std. — 2014-07-01
• Clock-setting standard: Abbr. — 2014-05-05
• BBC std. — 2014-03-30
• Frequent abbr. in BBC announcements — 2013-03-07
• Intl. standard — 2013-01-27
• Zero-deg. setting — 2012-04-14
• World clock std. — 2012-03-19
• Setting for BBC reports, in brief — 2011-07-22
• Certain world std. — 2011-06-30
• Prime meridian hrs. — 2010-10-02
• See 63-Across — 2010-09-19
• Std. in chronometry — 2010-08-20
• Clock setting at 0 degrees longitude: Abbr. — 2008-09-24
• London hrs. — 2008-05-19
• Chronometric std. — 2007-03-23
• Intl. standard — 2006-04-05
• Frequent abbr. in BBC announcements — 2005-07-10
• Chronometric inits. — 2005-04-16
• You can set your watch by it: Abbr. — 2004-04-22
• Clock standard: Abbr. — 2003-12-17
• Zulu, in the military: Abbr. — 2003-05-03
• Clock std. — 2002-11-01
• Clock std. — 2001-11-16
• Clock standard: Abbr. — 2001-04-27
• Clock-setting std. — 1998-04-30
• All clocks are set by it: Abbr. — 1997-08-06
• Prime meridian std. — 1996-03-03