I ran ncal -p to print the switching days from the Julian to the Gregorian Calendar, and I see this:
AL Albania 1912-11-30 IT Italy 1582-10-04
AT Austria 1583-10-05 JP Japan 1918-12-18
AU Australia 1752-09-02 LI Lithuania 1918-02-01
BE Belgium 1582-12-14 LN Latin 9999-05-31
BG Bulgaria 1916-03-18 LU Luxembourg 1582-12-14
CA Canada 1752-09-02 LV Latvia 1918-02-01
CH Switzerland 1655-02-28 NL Netherlands 1582-12-14
CN China 1911-12-18 NO Norway 1700-02-18
CZ Czech Republic 1584-01-06 PL Poland 1582-10-04
DE Germany 1700-02-18 PT Portugal 1582-10-04
DK Denmark 1700-02-18 RO Romania 1919-03-31
ES Spain 1582-10-04 RU Russia 1918-01-31
FI Finland 1753-02-17 SI Slovenia 1919-03-04
FR France 1582-12-09 SE Sweden 1753-02-17
GB United Kingdom 1752-09-02 TR Turkey 1926-12-18
GR Greece 1924-03-09 *US United States 1752-09-02
HU Hungary 1587-10-21 YU Yugoslavia 1919-03-04
IS Iceland 1700-11-16
Notice: LN Latin 9999-05-31. What does this mean? Why is it in the future? Why is it specifically on May 31, 9999? What is "Latin" (it's certainly not a country)?