No
Practically every country for business purposes.
Not a country, but Foula still uses the Julian calendar
You can use your 1999 calendar again in the year 2010. This is because both years start on the same day of the week and have the same leap year status. The cycle of calendars typically repeats every 28 years, though there can be exceptions.
A 2008 calendar can be used again in the years that have the same pattern of days as 2008. This occurs every 11 years, as long as the year is not a leap year. Therefore, the next year that has the same calendar pattern as 2008 will be 2019, and then again in 2030, 2041, and so on.
A Julian year is the same as a calendar year. We use a Gregorian calendar instead of a Julian calendar and have 3 fewer leap years every 400 years. Some Orthodox Churches follow a Julian calendar. They celebrate Christmas later than other Christians.
No. Much of the world uses the Julian calendar, which includes an extra day in Leap Year, and the Hebrew calendar includes a leap MONTH every few years, but the Islamic calendar does not. However, even in the parts of the world that use traditional non-Julian calendars, the standard western calendar is understood and used for the purposes of most international commerce and communications needs.
The next time the 1996 calendar can be reused is in 2024.
The answer is a calendar. Each month, the date changes regardless of how actively or minimally the calendar is used.
The Gregorian calendar is the calendar we use today. So, yes, it does have 12 months.
The ISO calendar is primarily a fiscal calendar and does not change the names of the days of the week, although it does number them differently, starting with 1 on Monday and ending with 7 on Sunday, however Monday on the ISO calendar is also the same Monday on the Gregorian calendar (day 2) and the same Monday that is on the Jewish calendar. Shabbot (or Saturday) does not change. It is still on the same day. But all that is really not relevant, as the keeping of Shabbot is based on the command in the Torah which is based on the Hebrew calendar. So it would not matter what calendar was in use by any country, even if it did mess with the definition of the week, the Hebrew calendar remains the same.
You can next correctly use your 1993 calendar in the year 2004. This is because both years start on the same day of the week and have the same leap year pattern. After 2004, the next times you can use the 1993 calendar again will be in 2015 and 2021.
Most countries use the Gregorian calendar, as the U.S. does. However some cultures use calendars that apply the same rules as the Gregorian calendar does. One example would be the Chinese Leap year, which adds a leap month about every three years. The placement of this leap month varies from year to year, and the name of the month is the same as the month preceding it.The Iranian calendar adds a leap day every four years as well, however every 6 or 7 years, the leap day is added on the fifth year instead of the fourth. The Iranian calendar, which only needs correction every 141,000 years, is more accurate than the Gregorian calendar, which needs correction about every 3226 years.Other examples include the Jewish (which also adds a leap month, Adar I), Hindu, Islamic, Baha'i (which adds a leap day to the last month every four years), and Ethiopian calendars. As far as I can tell, pretty much every country has a form of leap year.