My son is 26 months and night trained the same time he day trained, a few weeks ago. I think that might be unusual, though. He goes about 9 hours without peeing.
I wouldn't worry, I know I was one who day potty trained at 2, but I remember still wearing a diaper to bed until I was 4 or 5. And I'd wake through the night for a couple years after that, sleep walking and needing to go pee. I think it is all within the range of normal.