The BBY/ABY calendar existing in-universe.
Why do you hate it? I do not mind it.
Why would the New Republic establish a new year 0? Isn’t that something totalitarian regimes do? Why not use whatever year 0 the Valorum-era Republic used?
The New Republic did not see itself as just a continuation of the Old Republic; it saw itself as a major improvement, something new and better. The Old Republic, especially in its final years, was bloated, bureaucratic, and too weak to prevent the rise of Palpatine. So from the New Republic’s point of view, there was no reason to go back to that exact model. Therefore, creating a new calendar, with a new Year 0, was a symbolic way of saying, “This is a fresh start.” It helped to draw a clear line between what came before — the corruption of the late Republic, the dark times of the Empire — and what they hoped to build. And if you think about it, choosing their Year 0 around the time of the first real victory against the Empire makes emotional sense too. That moment was not just a military victory; it was the first time in years that people across the galaxy had real hope. From the New Republic’s perspective, that hope was the foundation of everything they were trying to build. So starting a new calendar from that moment sends a message: “This is when things began to change.”