Dates in GEDCOM files can be prepended with a “Date Escape” which defines the calendar notation of the date. The specification lists 6 Data Escapes:
- @#DGREGORIAN@ – The Gregorian calendar, also called the Western calendar and the Christian calendar, is internationally the most widely used civil calendar. When no Date Escape is used, the Gregorian calendar is assumed (default).
- @#DJULIAN@ – The Julian calendar was the predominant calendar in the Roman world, most of Europe, and in European settlements in the Americas and elsewhere, until it was refined and superseded by the Gregorian calendar.
- @#DHEBREW@ – The Hebrew or Jewish calendar is a lunisolar calendar used today predominantly for Jewish religious observances.
- @#DFRENCH R@ – The French Republican Calendar or French Revolutionary Calendar was a calendar created and implemented during the French Revolution, and used by the French government for about 12 years from late 1793 to 1805, and for 18 days by the Paris Commune in 1871.
- @#DROMAN@ – “for future definition”
- @#DUNKNOWN@ – when the calendar is unknown
In Analysing 635M lines of GEDCOM I did not count the usage of the different calendars. Now I did.
Within the nearly 7 thousand GEDCOM files of all Genealogie Online users there are 82,9 million DATE lines. The Date Escape usage is as follows:
- @#DGREGORIAN@ – 0
- @#DJULIAN@ – 10.201 (0,123 ‰) in files produced by Aldfaer, GensDataPro, Family Tree Maker for Windows, PRO-GEN, Brothers Keepers, Gramps, Heredis PC, Le Genealogiste & GeneWeb
- @#DHEBREW@ – 1.063 (0,013 ‰) in files produced by MyHeritage Family Tree Builder & GeneWeb
- @#DFRENCH R@ – 498 (0,006 ‰) in files produced by Family Tree Maker for Windows, MyHeritage Family Tree Builder & GeneWeb
- @#DROMAN@ – 0
- @#DUNKNOWN@ – 0
The very low numbers surprised me. Don’t all family tree programs support various calendars (and correct GEDCOM export)? Do the users not know about the various calendars? Or does everyone, in case of dates in other calendars, just convert the date to the Gregorian calendar with a calendar converter?