The Celtic calendar has 13 months, not 12, and each month does not have a variable number of days as in the Gregorian calendar; all months have an equal number of 28 days. The Celtic calendar is based on lunar cycles and natural events. Since 13 months are considered 28 days, 1 year corresponds to 364 days and the remaining one day is considered a ‘balance day’. The moon completes a full cycle around the earth in 29.5 days, which corresponds to 12.37 lunar cycles in a year. For this reason, 1 year is considered as 13 months.

In this calendar, each month represents a tree. This system is associated with the ‘ogham alphabet’ and tree symbolism. This calendar also divides the year into four parts, reflecting the passage of the seasons and natural phenomena. The Celtic year begins with the Samhain period, the end of summer and the end of the harvest, which is considered the beginning of winter (31 October to 1 November).

Following Samhain is the Imbolc period, representing the end of winter and the beginning of spring, a period considered to be the awakening of nature and the earth. Beltane (from 30 April to 1 May) is the period considered to be the full arrival of spring; Lughnasadh (from 1 August to 2 August= .

Celtic Tree Calendar Months and Trees

1. Birch 24 December — 20 January
Novelty, beginnings and purity. Hope and freshness after life’s difficulties.

2. Ash Tree (Rowan) 21 January — 17 February
Protection, wisdom and psychic power. It is seen as a shield against evil.

3. Tree Poplar (Ash) 18 February — 17 March
Connections, inner strength and harmony. A bridge that connects all areas of life.

4. Alder 18 March — 14 April
Courage, resilience and leadership. The power to cope with difficult situations.

5. Tree Willow 15 April — 12 May
Emotional balance, intuition and flexibility. Associated with the moon and water elements.

6. Tree Hawthorn 13 May — 9 June
Transformation, love and protection. Symbol of spring and fertility.

7. Tree Oak 10 June — 7 July
Strength, courage and endurance. It is seen as a sacred tree.

8. Tree Holly 8 July — 4 August
Energy of protection, strength and masculinity. It represents the endurance of winter.

9. Tree Hazelnut Tree (Hazel) 5 August — 1 September
Wisdom, knowledge and inspiration. It is considered sacred by the Druids.

10. Tree Vine 2 September — 29 September
Variety, wine and abundance. It symbolises the harvest season.

11. Tree Elm (Ivy) 30 September — 27 October
Commitment, endurance and growth. It represents progress despite difficulties.

12. Tree Reed 28 October — 24 November
Mystery, knowledge and depth. A means of accessing hidden things in nature.

13. Tree Pine Tree (Elder) 25 November — 23 December
Transformation, renewal and protection. The end and beginning of the life cycle.

Solstices and Equinoxes

Some special periods are associated with sacred trees outside the calendar:

Hornbeam (Poplar): Equinox periods.

Oak: Summer solstice.

Holly: Winter solstice.