Just wondering if it's right to say "What time is the concert?", "What time did you have lunch?" or should be "At what time is the concert? At what time did you have lunch?".
Both are 'correct' in everyday speech, but the second sentence is more formal because it is so grammatically correct. You will hear police officers in TV shows, questioning people, and saying, "At what time did you arrive at the hospital?"
A friend would say to another who is just leaving for work, "What time will you be home tonight?"