Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!

Qenya 

tanárea

adjective. *that old, that long lasting

The correlative ᴹQ. tanárea appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/108), a combination of ᴹQ. ta “that” and an adjectival form of ᴹQ. are “day”.

Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. tanaurëa “that old, that long lasting, (lit.) of that many days” using Q. aurë for “day”.