The religious interdictions mentioned by Caesar (vi. 13) may be regarded as tabus, while the spoils of war placed in a consecrated place (vi. 18), and certain animals among the Britons (v. 12), were clearly under tabu.
 Joyce, OCR 332 f.
 Book of Rights, ed. O’Donovan, 5.
 Book of Rights, 7.
 Ibid. 3 f.
 LL 107; O’Grady, ii. 175.
 In Highland tales geasa is translated “spells.”
 RC xxii. 27 f. The story of Da Choca’s Hostel has for its subject the destruction of Cormac through breaking his geasa (RC xxi. 149 f.).
The Celtic year was not at first regulated by the solstices and equinoxes, but by some method connected with agriculture or with the seasons. Later, the year was a lunar one, and there is some evidence of attempts at synchronising solar and lunar time. But time was mainly measured by the moon, while in all calculations night preceded day. Thus oidhche Samhain was the night preceding Samhain (November 1st), not the following night. The usage survives in our “sennight” and “fortnight.” In early times the year had two, possibly three divisions, marking periods in pastoral or agricultural life, but it was afterwards divided into four periods, while the year began with the winter division, opening at Samhain. A twofold, subdivided into a fourfold division is found in Irish texts, and may be tabulated as follows:—
Geimredh, beginning with the
A. Geimredh festival of Samhain, November 1st.
2nd quarter, Earrach, beginning February
1st (sometimes called Oimelc).
Samradh, beginning with the
B. Samhradh festival of Beltane, May 1st (called also
(summer half) Cet-soman or Cet-samain, 1st day of
Samono-s; cf. Welsh Cyntefyn).
Foghamhar, beginning with
the festival of Lugnasadh, August 1st
(sometimes called Brontroghain).
These divisions began with festivals, and clear traces of three of them occur over the whole Celtic area, but the fourth has now been merged in S. Brigit’s day. Beltane and Samhain marked the beginning of the two great divisions, and were perhaps at first movable festivals, according as the signs of summer or winter appeared earlier or later. With the adoption of the Roman calendar some of the festivals were displaced, e.g. in Gaul, where the Calends of January took the place of Samhain, the ritual being also transferred.