You can argue until the wee hours every night for a year, but a divorce is not pending until one spouse files initiating paperwork with the appropriate court. The documents -- a summons and petition or complaint for divorce -- officially begin the divorce action. Once those papers are served on the other spouse in the manner required by court rules, litigation is underway.
Terminating a Divorce
Your divorce is no longer pending when the court issues its final judgment or order of divorce and the time period for post-judgment motions and appeals has passed. The timing varies among jurisdictions and between litigants. Some states, like California, require that at least six months pass between the filing and final judgment, which can increase the period during which the divorce is pending.