Qenya
mallume
adverb. at what time, at what time, *when
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!
The correlative ᴹQ. mallume “at what time” appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/109), a combination of interrogative ᴹQ. ma and ᴹQ. -llume “time”.
Neo-Quenya: For purposes of Neo-Quenya, I would use mallume as the basic Quenya interrogative for “when”. There are other words for “when” appearing in DRC such as ᴹQ. má or ᴹQ. man(an), but they have issues: colliding with other words and/or using elements that are probably abandoned. Prior to the publication of PE23, I recommended using ᴺQ. malumë “when” modeled after silumë “now, at this time” and talumë “then, at that time”, but I now to prefer to use the form of the word proposed by Tolkien himself.