This article is about the practice where a date is given with reference to two calendars. For the practice where two couples sit side by side, see Double date.
On this marriage certificate, made out in 1907 in Warsaw (then part of the Russian Empire), the month is given as "November/December", and the day as "23/6". The Julian date 23November corresponded to the Gregorian 6December.
Excerpt of the cover page of a print of the Treaty of Lübeck (1629), with the Gregorian day (22) directly above the Julian (12), both before the name of the month, May. The treaty was concluded between Roman Catholic parties, who had adopted the Gregorian calendar, and Protestant parties, who had not.
Dual dating is the practice, in historical materials, of indicating a date with what appear to be duplicate or excessive digits: these may be separated by a hyphen or a slash, or placed one above the other. The need for dual dating arose from the transition from an older calendar to a newer one. Another method used is to give the date of an event according to one calendar, followed in parentheses by the date of the same event in the other calendar, appending an indicator to each to specify which reference calendar applies.
As an example, in the date "10/21February 1750/51" – a style seen in the records of Great Britain and its possessions – the notation arises from the prospective or previous adoption of the Gregorian calendar and a concurrent calendar reform. (The dual day number is due to the eleven days difference (at the time) between the Julian calendar date and the Gregorian one; the dual year is due to a change of start of year, from 25March to 1January.)
Dualdating is the practice, in historical materials, of indicating a date with what appear to be duplicate or excessive digits: these may be separated...
calendar changes, writers used dualdating to identify a given day by giving its date according to both styles of dating. For countries such as Russia...
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material...
calendar changes, writers used dualdating to identify a given day by giving its date according to both styles of dating. For countries such as Russia...
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive...
Chronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located...
Potassium–argon dating and argon–argon dating. These techniques date metamorphic, igneous and volcanic rocks. They are also used to date volcanic ash layers...
chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy. Absolute dating provides a numerical age...
radiocarbon dating, the reference date is January 1, 1950 (though the specific date January 1 is quite unnecessary, as radiocarbon dating has limited...
measurement. Geochronology Luminescence dating Rehydroxylation dating Thermoluminescent dosimeter Thermoluminescence (TL) dating Archived 2015-04-02 at the Wayback...
radiometric dating in the early 20th century, which provided a means of absolute dating, archaeologists and geologists used relative dating to determine...
Luminescence dating refers to a group of chronological dating methods of determining how long ago mineral grains were last exposed to sunlight or sufficient...
Nitrogen dating is a form of relative dating which relies on the reliable breakdown and release of amino acids from bone samples to estimate the age of...
Amino acid dating is a dating technique used to estimate the age of a specimen in paleobiology, molecular paleontology, archaeology, forensic science,...
Albinus Basilius. Soon afterwards, imperial regnal dating was adopted in its place. Another method of dating was ab urbe condita (Latin for "from the founding...
radiometric dating, the technique can be used to construct and calibrate the geomagnetic polarity time scale. This is one of the dating methodologies...
subject to taxation on worldwide income, etc.). Some countries do not permit dual citizenship or only do in certain cases (e.g., inheriting multiple nationalities...
The ISO week date system is effectively a leap week calendar system that is part of the ISO 8601 date and time standard issued by the International Organization...
between calendars and for some time afterwards, dualdating was used in documents and gave the date according to both systems. In contemporary as well...
introduced by Muslim astronomers in the 8th century to predict the approximate date of the first crescent moon, which is used to determine the first day of each...
systems in the Ancient Near East were based on the Babylonian calendar dating from the Iron Age, among them the calendar system of the Persian Empire...
and died possibly after 1229. The term is often used in art history when dating the career of an artist. In this context, it denotes the period of the individual's...
use of the Anno Passionis (AP) dating system which was in common use as well as the newer AD dating system. The AP dating system took its start from 'The...
"phantom time" added. Archaeological remains and dating methods such as dendrochronology (tree-ring dating) refute, rather than support, "phantom time"....
tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them...
A calendar date is a reference to a particular day represented within a calendar system. The calendar date allows the specific day to be identified. The...
dating was first used in 1949. Beginning in 1954, metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating,...
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