Sometimes conflated with old and new style dates—possibly because in England the two were both adopted around the same time—is the day on which the new year began. The west now use 1 January as the first day of each year, which is term Modern Style. This wasn’t always the case; prior to 1752 in England, the new year started on 25 March. This is is termed Annunciation Style or Lady Day Style. Scotland adopted the Gregorian calendar in 1752, but had started using Modern Style year numbering in 1600. As with new style, dates, modern style year numbering began in different times in different places, for example, in France, the Edict of Roussillon stated that from 1564, the new year was to start on 1 January—prior to that it had been reckoned differently in various regions of the country, some including: Christmas Day, 1 January (the Feast of the Circumcision), 25 March, Holy Sunday and Easter. To make matters more complicated, as Easter moved each year, if it was later the following year, than the previous, some dates between occurred twice in the same year.
Even in England, sometimes certain people had adopted the modern style numbering early than 1752, so the only way to tell is from context in an original document, such as when the year changes in a range of parish register entries.
To allow for modern style, vs. the various other styles, it is customary to use dual years, so it is clear that this has already been taken into consideration. This was even sometimes done at the time.
Pedigree Forge allows entering of both years, for example:
2 Feb 1644/5
Would indicate that this event took place in 1645 modern style, but is recorded in the original document as 1644. If only a single year is given, it is assumed the conversion to modern style has already been applied.
Technical Note 1: Dual dates are supported in GEDCOM in the Gregorian calendar, but they are only really used with the Julian calendar, which is an error in the GEDCOM specification. Pedigree Forge dual dates are exported and imported to GEDCOM in either calendar. Version GEDCOM version 7 does not support dual dates. When version 7.0 export is requested, the dual date is exported as a phrase, and the modern (generally higher) year is used. Dual dates are not automatically converted to “Old Style” as this risks automatic conversion of only around a quarter of the dates, which would potentially cause logic errors compared with the non-dual dated (and therefore non-converted) dates.
Technical Note 2: It would be desirable to reject when dual years are given after 25 March 1752, and only for dates between 1 Jan and 24 March, but this is an over simplified view, and is location dependent. These dates are therefore accepted, but warnings are issued in the form of “balloon tooltips” and in validation reports, which also take into consideration knowledge of the place where the event took place. General warnings are issued if the place can’t be determined, or if there is no knowledge of the convention in a particular place.
Technical Note 3: Most of the dates used for the first day of the new year are “after” 1 January, so modern style is the year with the higher value, for example 14 February 1600/01. However, in “Christmas Style”, i.e. new year before 1 January, the modern year is the lower of the two values. This isn’t covered by the GEDCOM spec, but the logical extension is that it is the second year that is the “modern” style year, and the first year that is the “original” year. So, a “Christmas Style” date would look like: “27 Dec 1532/1”. This is how Pedigree Forge handles “Christmas Style” years. Warnings are always issued when the second year (modern) is lower than the first (local).
Technical Note 4 Leap year dates are validated correctly and rejected. This does prevent 30 February 1712 from being accepted—it is an illegal date in both Gregorian and Julian calendars but is a legal date in the Swedish calendar, due to the way that the transition was first handled.