quantien ("q") noun "last day of year" (YEN) or "full year" (VT46:23). The latter gloss also turns up in PM:quantien "full year" = yén, a period of 144 solar years (PM:126; pl. quantiéni, PM:127). Since the latter meaning comes from drafts for the LotR Appendices that did not make it into the published LotR, it is difficult to tell whether it is canonical.
Quenya
yén
long year
yén
noun. Elvish long year (144 solar years)
quantien
last day of year
yén noun, Elvish "long year" of 144 solar years, 52,596 days (Nam, Appendix D, E; RGEO:66. Tolkien earlier defined yén_ as 100 solar years; see PM:126. In the Etymologies, stem YEN, it seems to mean simply "year", but in the LotR Appendices the word for "year" instead appears as _loa or coranar, q.v.) Yénonótië "reckoning of years" (MR:51). Pl. yéni in Nam and Etym, entry YEN though the plural form is misread as "yen-" in the printed version of the Etymologies, cf. VT46:23. Yéni pa yéni "years upon years" (VT44:36). Pl. genitive yénion in yénion yéni "ages of ages" (VT44:36)