Counting time in History

For historians, counting time is basic for having a good understanding of the past. It is really important to put in the correct order the events for investigating the relations that exist between them. However it is important to remember that, depending on the culture, it has changed through time. Nowadays, in western countries, we use the birth of Jesus as reference; however, other cultures likes chinese one, use another types of calendar and references. 

We start counting in year 1 (Birth of Jesus) and we use the initials B.F. (before Christ) for referring to the years previous to this event and A.D. (Anno Domini) for the years after his birth. The year 0 doesn't exist. Thanks to this, we can can organize correctly the historical events and processes. 

Exercise 1. Put in the correct order the following dates. 

A. D. 133
25 B.C.

1100 B.C.

427 A.D.
1492 B.C.

In History, we also use word like decades, centuries or milleniums. A decade is a period of 10 years, a century refers to 100 years and a millenium to one thousand years. It is really usual to see the centuries as a cronological reference. For calculating the century of a year, cover the last two numbers up and add one. 

Exercise 2. Calculate the centuries of the following years: 

A.D. 333

756 B.C

A.D. 1085

A.D. 473

1250 B.C.