Re: Is " in a cold winter day " correct?
Bear in mind that the quote was spoken by Mandla Mandela, a South African national whose native language is (I believe) Xhosa. His second language is English and he probably also speaks Afrikaans (his grandfather studied Afrikaans so it's possible). It is possible that "in a cold winter day" is natural in South African English or he simply made a slip. It is also possible (but unlikely) that the BBC transcript of the quote contains an error. It is easy to type "in" when you mean "on" because "I" and "O" are next to each other on the keyboard.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.