Hi Emperor哈里. In terms of meaning, there is no difference between 'about' and 'or so'. Both work well for saying how many minutes/hours/days, but I think when you talk about specific times (5 o'clock, 1999, the 10th of January), though, 'or so' sounds a bit strange. You should just use 'about' or 'around' to be safe for these kinds of expression of time. By the way "We have to leave about in five minutes" should be "We have to leave in about five minutes". Hope that helps. Neil