Expressions A time line is a useful way to represent important dates and events throughout history. It's common to d historical time line into events that occurred either BC (to the left of zero) or AD (to the right of zero). The you're living in right now takes place in AD. BC AD 0 When performing mathematical operations involving dates, we can think of a historical time line as a nur On the number line, the years increase from left to right. If zero represents the origin, the years to the rig are considered positive numbers and the years to the left of zero are considered negative numbers. Usir analogy, here are some events that might appear on a historical number line: Event Historical Time Line Number Line The first ancient games take place in Olympia, Greece. 776 BC -776 Construction begins on the Great Wall of China. 221 BC -221 World War I begins in central Europe. AD 1914 1,914 (or 1914) Use these ideas about time lines and number lines to answer the questions that follow.