esbat provides functions for lunar phase calculations.

The algorithms are as published in Calendrical Calculations: The Ultimate Edition by Edward M. Reingold and Nachum Dershowitz, used with permission. The book notes:

... the algorithms are centered around the present date, for which they are accurate to within about 2 minutes. Their accuracy decreases for the far-distant past or future.

This crate uses a non-commercial license, a Creative Commons Attribution-NonCommercial 4.0 International License, at the request of the authors of Calendrical Calculations. Please contact the author of this crate at iliana@buttslol.net for any licensing questions.