Introducing LichTa: An Open-Source Lunar Calendar Library

Vietnamese lunar calendar calculations look simple until you actually try to implement them. Between astronomical timezone quirks, leap month rules, and decades of inconsistent public data, most developers either hardcode a lookup table that breaks in a few years or give up and skip lunar dates entirely.

LichTa is our answer: a small, dependency-free library that calculates the Vietnamese lunar calendar directly, instead of relying on static tables. It powers the upcoming Sổ Âm Lịch app in Cuonso Apps, and we're releasing it as open source from day one because this is exactly the kind of infrastructure that shouldn't be locked inside one product.

@lichta/core is available on npm and GitHub right now. If you're building anything that touches Vietnamese dates — a calendar app, an e-commerce site that needs lunar holidays, a cultural app — we'd genuinely like to hear what you build with it.

This is also a preview of how we plan to open-source parts of the Zeforc ecosystem going forward: the pieces that are genuinely reusable infrastructure, not just marketing gestures.