What are the two ways to be a citizen by birth?

There are two general ways to obtain citizenship through U.S. citizen parents: at birth, and after birth but before the age of 18. Congress has enacted laws that determine how citizenship is conveyed by a U.S. citizen parent (or parents) to children born outside of the United State.

europe would not recognize the confederacy as an independent nation.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.