Silpion

This figure of 14,325 (solar) years is calculated from dates given in 'Valian Years' in The Annals of Aman (in volume X of The History of Middle-earth). It might seem precise, but Valian Years are much longer than solar years, and the source material underwent considerable revision. So, while not completely reliable, this figure gives some idea of the kind of timespan for which Silpion gave its Light to the land of Valinor.

A full interpretation of this name Silpion is difficult, though it clearly contains the element sil-, 'shine' (especially with a white light, as would be appropriate for this White Tree). In volume IV of The History of Middle-earth, in notes to The Earliest Annals of Valinor, Tolkien provides an interpretation into Old English, which might point toward to the Elvish name's meaning. The Old English version of Silpion is Glisglóm, which combines the words for 'shining' and 'twilight'. On that basis, we might tentatively interpret the Elvish name in the same way, though it cannot be guaranteed that the Old English form represents an absolutely literal translation of the name.