How long were roman numerals used for?

Answer 1

Roman numerals were largely abandoned during the 14th century, in favour of Arabic numerals (1, 2, 3, etc). Unlike Roman numerals, Arabic symbols are positional and include the digit 0, and are therefore much easier to work with when working with number mathematically.

However, Roman numerals are still in use today. Introductory pages in a book (prefaces) typically use lower case Roman numerals to differentiate them from the main pages of the book which use Arabic numerals. Where a book is made of two or more separate books, each book is often numbered with upper case Roman numerals, as in The Lord of the Rings, Book II: The Two Towers. Many analogue clock faces also use Roman numerals. We also denote years with Roman numerals, as seen during the end credits of feature films and TV productions. We also use them when listing items using ordinal linguistics (first, second, third, etc) and when referring to lineage, such as "King Louis XIV" and "Queen Elizabeth II". (To avoid confusion between the person and the boat of the same name, we usually refer to the person as "Queen Elizabeth the second", while the boat is referred to as "Queen Elizabeth Two" (or "QE2" in abbreviations)).