To calculate the year that was 5 billion years ago, we can subtract 5 billion from the current year. Since the current date is 2023, we can perform the calculation as follows:
2023 (current year) - 5,000,000,000 (5 billion years) = -4,998,000,977
Therefore, approximately 5 billion years ago was around the year -4,998,000,977. It's important to note that using negative years is a way to denote time before the common era (BCE) or before the year 1 CE.