Calendars and time

Double Dating

Direct answer

Double Dating writes two date or year labels for one event when calendars or new-year conventions overlap.

Double Dating records both of two competing historical date conventions.

Calendars & TimekeepingThe Great Almanac DictionaryUpdated 2026-09-26

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At a glance

Found in: Calendars & Timekeeping
Related: New Style Date, Calendar, Julian Date, Coordinated Universal Time

An engraved clock movement with an hourglass and a sundial — Calendar and clock · visual guide **Double Dating**
Double Dating records both of two competing historical date conventions.
A cycle or timeline schematic for comparing the named timekeeping concept.

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The story behind Double Dating

Writers often used paired years such as 1731/32 during periods when January and February could belong to different numbered years by different conventions.

Why Double Dating matters

Double Dating preserves source accuracy while helping modern readers follow chronology across a calendar transition.

Double Dating in practice: an example

A record dated February 10, 1731/32 signals that the old legal year and modern January-start year disagree.

Where readings of Double Dating go wrong

It is a mistake to interpret a slash year as uncertainty; it can be a precise statement of two recognized systems.

Sources and editorial method

Research references used for this entry include:

U.S. Naval Observatory: Introduction to Calendars - Official overview of calendar systems, leap rules, eras, and historical calendar reform.

Source: The Great Almanac Dictionary
Category: Calendars & Timekeeping
Last updated: 2026-09-26

Preserve both historical labels

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New Style DateA New Style Date converts a historical date to the newer calendar convention. CalendarA Calendar organizes days into named and numbered cycles for reckoning time. Julian DateJulian Date is a continuous astronomical count of days and day fractions. Coordinated Universal TimeCoordinated Universal Time is the international reference standard for world time. Sidereal TimeSidereal Time is star-based rotational time used to orient the sky. Old Style DateAn Old Style Date preserves a pre-reform calendar convention.

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