There are 'bible reading planners' available that give you a couple of chapters to read each day. On 'average' this amounts to about 20-30 minutes a day. Using that, it's possible to read both the whole of the Old Testament once and the whole of the New Testament twice in a calendar year.
A friend of mine at uni decided that to read the bible from start to finish. I seem to recall that it took him about five to six weeks (but he was doing more than 20 minutes each day, he was a dossy student).