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tychonievich merged 6 commits into from
Aug 26, 2026
Merged

Add Swedish calendar #799

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569d866
Fixes #28
tychonievich Aug 19, 2026
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tychonievich Aug 19, 2026
443881f
rewrite for more clarity
tychonievich Aug 19, 2026
f0926d6
Change wording to emphasize actual use rather than original plan
tychonievich Aug 19, 2026
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tychonievich Aug 26, 2026
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tychonievich Aug 26, 2026
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30 changes: 29 additions & 1 deletion specification/gedcom-6-appendix-calendars.md
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Expand Up @@ -2,7 +2,7 @@

## Known Calendars

This specification defines 4 calendars: `GREGORIAN`, `JULIAN`, `FRENCH_R`, and `HEBREW`.
This specification defines 5 calendars: `GREGORIAN`, `JULIAN`, `SWEDISH`, `FRENCH_R`, and `HEBREW`.
Previous versions also provided for, but did not define the meaning of, `ROMAN` and `UNKNOWN` calendars.

Extension calendars should use the usual rules for extensions, including using `_` as the leading character of the calendar name.
Expand Down Expand Up @@ -56,6 +56,34 @@ Thus, there is no year 0; year 1 BCE was followed by year 1.

The URI for this calendar is `g7:cal-JULIAN`


### `SWEDISH`

The Swedish calendar was introduced by the government of Sweden in 1700 and used until 1712.
It is the same as the Julian calendar except it omitted leap day in 1700 and added a second leap day as 30 February 1712;
between those dates the Swedish calendar was 1 day ahead of the Julian calendar.

:::note
While the Swedish calendar was only official in use from 1700 to 1712,
some sources might reference it outside of those dates
as a synonym for the Julian calendar.
Such dates should be represented using `JULIAN`, not `SWEDISH`.
:::

This calendar uses the same months as the Julian and Gregorian calendars, differing only in the number of days in February:

| Year | Days in Feb | Note |
|------|-------------|-----------------------------------------------------|
| 1700 | 28 | Leap day omitted in 1700 |
| 1704 | 29 | |
| 1708 | 29 | |
| 1712 | 30 | The leap day omitted from 1700 reinserted as 30 Feb |

This calendar was in use from 1700 to 1712. Thus, no epoch marker is permitted in this calendar.

The URI for this calendar is `g7.1:cal-SWEDISH`

@dthaler dthaler Aug 19, 2026

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Suggested change
The URI for this calendar is `g7.1:cal-SWEDISH`
The URI for this calendar is `g7.1:cal-SWEDISH`.

@dthaler dthaler Aug 19, 2026

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The other sections have this similar lack of ending punctuation, so maybe handle in a separate PR



### `FRENCH_R`

The French Republican calendar or French Revolutionary calendar are the names given to the new calendar adopted in 1794 by the French National Convention. This calendar was adopted on Gregorian day 22 September 1792, which was 1 Vendémiaire 1 in this calendar. It was abandoned 18 years later.
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