Who was Christ to Atheists/Scientists?

So I know scientists aren't much on the believing in God stuff but I am genuinely curious onto why they use Christ as a reference of time, I find it kind of odd for them to use the name of a person they don't believe has much importance, even if they believe Jesus was real what made Jesus so important to scientists that they made the time period before Christ BC? They could've used anything else couldn't they?

I'm a believer and a Christian so personally from my point of view it's obvious and makes perfect sense, BC is before Christ, using Christ to put a line on the timeline before the birth of Christ because it's a memorable moment for us that God came to earth, lived perfect and died for our salvation so having that to count time is actually kinda cool. Maybe the scientists that created the BC were Christians?
Who was Christ to Atheists/Scientists?
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