The answer is +2 days today's day.
I like to explain it with numbers: {1 [What day (today)] + 1(is the day) + 1 (after tomorrow)} so 1+1+1-1 (for today) all together is +2.
Since when you asked this question it was 5 Jan 2010 and that is a Tuesday then "What day is the day after tomorrow? " would be Yesterday (Thursday)
Hope this helped!! :)