Okay, the user wants me to translate "man-day" into Vietnamese. Let me think about the correct term here. "Man-day" is a unit of work, right? It refers to one person working for a day. In Vietnamese, the equivalent term is "ngày công". Let me confirm that. Yes, "ngày công" is commonly used in contexts like labor costs or project timelines. So the translation should be "ngày công". I need to make sure there's no other possible translation, but I don't think so. The user also mentioned if the content is already in Vietnamese, leave it as is. Since "man-day" is English, translating to "ngày công" is correct. Alright, that's the answer.