parakeet having babies

Question
I have a question my daughter has a female and a male and she just laid an egg last night which was 2/8/09 and we were wondering how long would it take to wait on it to hatch

Answer
Females don't usually start incubating until they have two or three eggs.  They lay one about every 18 hours, so by now she may have more.  Once the female starts incubating, start counting days.  Many budgie owners become frustrated because they count from when the eggs are laid, not when they are incubated.  The incubation period is normally 18 days.