Santa has a huge list of good children that he maintains, complete with addresses and even zip (postal) codes. The list, of course, gets bigger each year by virtue of the world's increasing population. Santa has had to adapt over the years to having less and less time to deliver his toys. If one were to assume he works in the realm of standard time as we know it, clearly he would have perhaps 2-3 ten-thousandths of a second to deliver his toys to each child in the world who believes in Santa!
The fact that Santa Claus is more than 15 centuries old and does not appear to age is our biggest clue that he does not work within time as we know it. His Christmas Eve trip may seem to take around 24 hours, but to Santa it could be that it lasts days, weeks or months. Santa would not want to rush the important job of bringing Christmas happiness to a child, so the only logical conclusion is that Santa somehow functions on a different time and space continuum.