“Doesn’t say here: when did you graduate high school?”
Read: “I can’t gauge by looking and I need to find a way to ask ‘how old are you?’ without being slapped with an age discrimination suit.”
How to respond: If you feel comfortable with disclosing your age, go ahead and give the year. If you don’t, no problem- a lady never tells right? Answering with something vague like “it feels like ages ago” is absolutely fine. It will be good cause for you and your interviewer to pause and chuckle and a good time for you to get around the question by quickly describing your first real work experience.