adverb
how long; until when
Asks about the duration or endpoint of a state or action. Often used in questions or with ～か to form indirect questions.
いつまでここにいるつもりですか。
How long do you plan to stay here?
この雨はいつまで続くんだろう。
I wonder how long this rain will last.
Compound of いつ (when) and まで (until). The kanji spellings are ateji and rarely used.