Absolutely 🙂

Yes, you can absolutely use "at" in conjunction with "ten to six." The sentence "The train comes at ten to six" is perfectly correct and understandable. In this context, "ten to six" refers to the time 5:50, and using "at" helps specify the exact moment when the train is expected to arrive. This kind of expression is commonly used to describe time, especially in informal conversations.

Hi Okami, I apologize for my very late response! Many other teachers have already answered your question. I’ll add that I believe most people these days just say five-fifty. BUT if you said ten-to-six then you’re showing a high level of English! Also using “at” is important.

I usually hear it said 5:50 or 17:50 military time but this is understandable and natural.

I have never heard anyone say this and so it briefly struck me as unfamiliar; however, I understand it perfectly, and so will every other native English speaker.