Possibly John the Apostle since he writes about it in Revelation 12.Who were the witnesses to this event?
At some point during the apostolic age. Scripture, nor Tradition give an indication as to a precise date of the event.When and where did it happen?
The IC of Mary was not defined until 1854. The Assumption of Mary was not defined until 1950. These two teachings would not have been an issue for the Protestant reformers.If the rcc had evidence that this event happened, they would have made it public and put an end to the protestant revolution once and for all.