When were women allowed to have multiple husbands without sin?
According to this answer, the Rishis permitted this practice at one point in history:
King Pandu well-acquainted with all rules of morality, replied ... But I shall now tell thee about the practices of old indicated by illustrious Rishis, fully acquainted with every rule of morality... women formerly were not immured within houses and dependent on husbands and other relatives. They used to go about freely, enjoying themselves as best as they liked ... they did not then adhere to their husbands faithfully, and yet, O handsome one, they were not regarded sinful
During what time period was this allowed?