pronoun
Emphatic interrogative pronoun meaning 'when', often used when the speaker is impatient or wants a specific date/time. Similar to いつ but more insistent.
いついつまでにこの仕事を終わらせればいいですか。
By when exactly do I need to finish this work?
いついつ来るって言ってたっけ？
When did he say he was coming again?
いつ is the standard 'when'; いついつ is more emphatic and often expects a concrete answer.
Reduplication of いつ (when) for emphasis.