PrintableCharts
LEAP SECONDS

1 / 3 · mockup · mid-century

LEAP SECONDS

27 seconds added to UTC since 1972, none since 2016 — the longest run there has ever been

Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.

Three sizes in one archive — from a sheet on the fridge to a poster on the wall.

Standard$1.50

Payment and email are handled by Paddle. The download link arrives by email — no account, no password.

Formats
A4 · A3 · A2
What you get
Print-ready PDFs, one per size, with every letterform converted to outlines — nothing to install, nothing to shift.
Subject
units · reference · study

Each step is one second added to UTC at 23:59:60 on the day named; TAI has no steps at all. The height of the stair is how far atomic time has run ahead of the turning Earth.

THE SECOND THAT HAS NEVER HAPPENED

Every one of the 27 was a second added. The grammar of RFC 3339 knows the other direction too: the seconds field runs 00-58, 00-59, 00-60, and 58 is there because a second taken away would leave the last minute of the day one second short. No clock has ever shown that value.

It may yet be needed. The IERS list itself explains the widening intervals since 2000 by "the acceleration of the Earth’s rotation speed", and Resolution 4 of the 27th CGPM (2022) names among its reasons for ending the practice "the possible need for the first negative leap second whose insertion has never been foreseen or tested".

On the sheet

  • Each step is one second added to UTC at 23:59:60 on the day named; TAI has no steps at all. The height of the stair is how far atomic time has run ahead of the turning Earth.
  • Colour carries meaning, but meaning never rests on colour alone — the sheet reads in black and white.
  • Nothing about how it was made: the sheet carries only what the reader needs.

Printing

  • Three sizes in the archive: A4 — 210×297 mm, A3 — 297×420 mm, A2 — 420×594 mm.
  • All text is converted to outlines. No fonts to install, and nothing shifts on another machine.
  • White background and sparing fills — it prints on a home printer without draining the cartridge.
  • Margins of at least 10 mm: a home printer cannot print to the edge.
  • No stroke thinner than 0.3 mm, so nothing disappears in print.

Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 9 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.

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