Historical Timeline Skill

Generate interactive historical timelines as self-contained HTML files powered by TimelineJS3.

Critical: Things Claude Won't Know Without This Skill

BCE dates use negative year numbers

{"year": -551, "month": 9, "day": 28}

This renders as "551 BCE". No special syntax — just negative integers. There is no year 0: -1 is 1 BCE and 1 is 1 CE (the builder raises ValueError for year 0). If your source gives astronomical years (where 0 = 1 BCE), subtract 1 from every year ≤ 0 first.

The scale property matters for ancient dates

For timelines spanning thousands of years or BCE dates, set "scale": "human" (the default). Use "scale": "cosmological" only for astronomical/geological timescales.