Ancient Rome did not use the counting system used throughout the world today. It used Roman numerals. They are combinations of letters from the Latin alphabet with different values.
Here is the Roman numeral system:
The number two is II. The number for four, however, is IV. Here the number one is subtracted from five. The number six is VI. The number one is added to five.
Here are different numbers in the Roman numeral system:
2012 (the current year) MMXII
1789 (the French Revolution) MDCCLXXXIX
2000 (the start of the 21st century) MM
52 (the number of weeks in one year) LII
365 (the number of days in one year) CCCLXV
The Roman numerals were used in the days of Ancient Rome. Though they no longer enjoy the popularity of former days, they are still used to number sporting events, in clocks and watches, and to number the chapters of books. This is a testament to their historical significance.