In the other examples, it depends on context. Where are you writing "Year 1 BC"?
An example from Wikipedia:
You might want to learn about Common Era, too - it is more acceptable around the world because it does not refer to Jesus.Gaius Julius Caesar (13 July 100 BC – 15 March 44 BC) was a Roman general and statesman. He played a critical role in the gradual transformation of the Roman Republic into the Roman Empire.
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