Swedish Calendar

Pages from a 1712 Swedish almanac, showing the month of February. Public domain. Available from Wikimedia Commons.

Sweden did not immediately change from the Julian calendar to the Gregorian calendar. On 1 March 1700, Sweden changed from the Julian calendar to the Swedish calendar. The plan was to skip all leap days between 1700 and 1740, until the Swedish calendar aligned with the Gregorian calendar. February 29 was skipped in 1700, but  because of the Great Northern War, no additional leap days were skipped. The Swedish calendar was a day ahead of the Julian calendar and ten days behind the Gregorian calendar.

In the leap year 1712, an extra day was added to the calendar. That year, there was a February 30 in Sweden. The Swedish calendar was then abandoned. Sweden adopted the Gregorian calendar in 1753.

References
February 30
Moveable Feast Day Calendar for Sweden
Swedish calendar