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.