About 75 days. That is assuming you and your spouse come to an agreement on all terms prior to the initial divorce hearing. Once the court grants the divorce, there is a 90-day waiting period. In some cases, the court will grant an expedited hearing for exceptional circumstances.
There are several factors which delay the process. Often there are disagreements about child custody or valuation of assets which take some time to sort out.
If you begin the process in divorce mediation, expect the mediation process to take 3 to 5 sessions to arrive at an agreement. The timeline for mediation is a function of your schedule and the mediators. I have completed mediations in a week, using marathon sessions, while other cases have taken three months to get through divorce mediation simply because of scheduling.
Divorce litigation is another story. Depending on contested issues, the process could take a year or more.
Keep in mind that even if there is not a final agreement or judgment most parties live apart as soon as the process begins. In many ways, living separate and apart during the divorce mediation process or divorce litigation process alleviates stress and anxiety.