How old is ATOM cosmos?

Could you please clarify for me the age of the ATOM cosmos? I'm interested in understanding its historical timeline, specifically when it was initially launched or established. I'm aware that cryptocurrencies and blockchain technologies are relatively new, but I'm curious about the specific timeline of ATOM's genesis and its journey so far. Is there a specific date or year that marks its inception? Also, how has it evolved and grown over time? Could you provide a brief overview of its significant milestones? Thank you for your assistance in answering my inquiry.