Celtic tree calendar
Glossary · Last updated: 2026-07-26
The Celtic tree calendar popularized by Robert Graves divides the year into thirteen periods, each associated with a tree (Birch, Rowan, Ash, etc.).
Scholars debate how much is ancient vs twentieth-century synthesis. Our app uses the common date table for accessible cultural exploration.
Thirteen moons
Some versions tie trees to lunar months rather than fixed Gregorian slices. We document the fixed-date mapping used in our calculator.