From start to finish, divorce usually takes around one year. This timeframe is for an uncontested divorce, where all parties are able to agree on all the issues for resolution. If the parties in the divorce can't agree on the terms of the settlement, then a trial must take place, where a judge decides the issues. A contested divorce, that's settled by a judge, can take much longer than a year.
Of course, a divorcing couple might seek the help of a mediator, a disinterested third party who hears both sides and offers advice on ways to come to a solution. Some states have rules about how long a divorce can take while others have higher rates of divorce and getting on the court calendar can slow the process, even contested divorces need to be approved by a judge.