What is the minimum time for mutual divorce???

as on date there is no waiver of 6 months period in mutual consent divorce and it is a must 

Mutual Divorce is to be filed by the couple only after they have lived apart for at least a year. A petition supported with affidavits for divorce should be filed in the district court by the both the spouses. The husband and the wife should jointly state to the court that they are unable to live together as they are facing immense difficulties in adjustment.

The filing of divorce petition by both the husband and the wife is legally known as the "The First Motion Petition for Mutual Consent Divorce". "The Second Motion Petition for Mutual Consent Divorce" mentioned in the sub-section (2) of Section 13 B is filed when the couple reappears to the court for the second time after a period of six months. If the judge is satisfied after a hearing from both the husband and wife, the court announces a mutual divorce decree.

Beautifully articulated by experts above, just to add and enrich, the second motion   submission must be before 18 months from the first create motion. However per MP high court if any petition on grounds of cruelty and desertion is pending, the court need not wait for the stipulated period ref AIR 2005 MP 106, Dinesh kumar v/s Neeta