Related Clues:

• All clocks are set by it: Abbr.
• Clock-setting std.
• Clock std.
• See 63-Across
• Clock standard: Abbr.
• Greenwich time zone
• Zulu, in the military: Abbr.
• London hrs.
• Zero-longitude hr.
• You can set your watch by it: Abbr.
• Time std.
• Chronometric inits.
• Frequent abbr. in BBC announcements
• Clock standard (Abbr.)
• Intl. standard