Free Excel Human Era
The calendar most commonly used today places year 1 CE at a point in time during the Roman Empire. That system labels earlier human accomplishment "before" or assigns negative numbers.
Emiliani's HE calendar places year 1 HE much earlier, when humans were settling into agricultural communities (loosely matching the beginning of the geological Holocene Epoch). Calling any point in time "year 1" is somewhat arbitrary. EMILIANI set 1 HE exactly 10,000 years before 1 CE.
With this calculator, you can convert between the BCE or BC and