As I know it depends on your eye sensitivity and whether you choose soft or rigid gas permeable contact lenses, it may take only a day or it could take two weeks or more for your eyes to adjust to the lenses. Some people's eyes never adjust, but that's rare.
probably takes about 3 weeks before you truly get used to them. When i first got contacts it took me about 30 minutes to put them in and 10 minutes to take them out. Now i can take them out in less than 20 seconds and put them in, in about 30 seconds. When you get used to them i always forget they are in and i have fallen asleep with them in numerous times because i forgot they were in my eye.