LunaZodiaco is a F# library to calculate moon phases and the zodiac sign of the moon for a given day. It calculates the ecliptic longitude at a reasonable accuracy. The moon phase is calculated using Conways method, which works in the 20th and 21st century and is accurate to about 1 day. Don't use both calculations for astronomical calculations where accuracy is needed, but it's good enough for a calendar.
$ dotnet add package LunaZodiacoNo README available.