Technically speaking I think it would be 4,997,978 BCE, but at that point you’re talking about geologic rather than anthropic timescales so you’d more likely just call it 5 mya (5 million years ago).
When we are talking about years that long ago, we typically just say mya (million years ago or Ma for mega annum), or Ga for giga annum (billion years), at least this is true in my line of study, which is geology. As @fondots explained above, 1CE is considered the birth yeah of Jesus, hence years before the common era being called BC, for before Christ, before BCE became more common. Since humans (at least as Homo sapiens) weren’t around 5 million years ago, as geologists, we don’t really consider those years to be part of the BCE year group.
Would that mean 5 million years ago it would be 5,000,2023 BC or is there some other format for dates that far back?
Technically speaking I think it would be 4,997,978 BCE, but at that point you’re talking about geologic rather than anthropic timescales so you’d more likely just call it 5 mya (5 million years ago).
When we are talking about years that long ago, we typically just say mya (million years ago or Ma for mega annum), or Ga for giga annum (billion years), at least this is true in my line of study, which is geology. As @fondots explained above, 1CE is considered the birth yeah of Jesus, hence years before the common era being called BC, for before Christ, before BCE became more common. Since humans (at least as Homo sapiens) weren’t around 5 million years ago, as geologists, we don’t really consider those years to be part of the BCE year group.