[skissane]

The traditional AD/BC system (aka the CE/BCE system) doesn't have a year zero. But astronomical year numbering does. (0 = 1 BC, -1 = 2 BC, etc.) Given the astronomical flavour of this discussion, the assumption that BetaCygni was using astronomical year numbering is reasonable.

https://en.wikipedia.org/wiki/Astronomical_year_numbering

[BetaCygni]

I'm just a developer who by habit starts counting from 0. I meant to start at January 1st AD 1 0:00 AM.