To unambiguously specify the date, dual dating or Old Style (O.S.) and New Style (N.S.) are sometimes used with dates. Dual dating uses two consecutive years because of differences in the starting date of the year, or includes both the Julian and Gregorian dates. Old Style and New Style (N.S.) indicate either whether the start of the Julian year has been adjusted to start on 1 January (N.S.) even though documents written at the time use a different start of year (O.S.), or whether a date conforms to the Julian calendar (O.S.) rather than the Gregorian (N.S.). 

The Gregorian calendar was a reform of the Julian calendar instituted in 1582 by Pope Gregory XIII, after whom the calendar was named, by papal bull Inter gravissimas dated 24 February 1582. The motivation for the adjustment was to bring the date for the celebration of Easter to the time of year in which it was celebrated when it was introduced by the early Church. Although a recommendation of the First Council of Nicaea in 325 specified that all Christians should celebrate Easter on the same day, it took almost five centuries before virtually all Christians achieved that objective by adopting the rules of the Church of Alexandria (see Easter for the issues which arose). QUESTIONS:

Q1:
1. What is the abbreviation of the term "Old Style"?
2. What two letters are used to abbreviate "Old Style"?
3. 
Q2:
1. What is the abbreviation of the term "New Style"?
2. What two letters are used to abbreviate "New Style"?
3. 
Q3:
1. How many consecutive years are used in dual dating?
2. What is the total number of consecutive years that are used in dual dating?
3. 
Q4:
1. What are the names of the dates that are included in dual dating?
2. Dual dating includes which two dates?
3. 
Q5:
1. The Old Style and New Style dual dating system is used to dictate the start of what calendar?
2. What calendar's starting date is dictated by the Old Style and New Style dating system?
3. 
Q6:
1. When does the Julian calendar begin?
2. What is the date when the Julian calendar begins?
3. 
Q7:
1. What is the name of the calendar that was reformed by the Gregorian calendar?
2. The Gregorian calendar reformed which other calendar?
3. 
Q8:
1. What year was the Julian calendar reformed into the Gregorian calendar?
2. The Gregorian calendar reform of the Julian calendar took place in what year?
3. 
