We do not know the exact date of Mary's Dormition. It could have occurred at anytime. If occurred after the completion of various books it would not be recorded, or if it occurred in the presence of someone that was not a writer of a biblical book the same holds true.
There is Biblical evidence supporting it.
Revelation 11:19 Then God’s temple in heaven was opened, and the ark of his covenant could be seen in the temple. There were flashes of lightning, rumblings, and peals of thunder, an earthquake, and a violent hailstorm.
Revelation 12:1-2 A great sign appeared in the sky, a woman* clothed with the sun, with the moon under her feet, and on her head a crown of twelve stars.
2 She was with child and wailed aloud in pain as she labored to give birth.
Do non-Catholics deny that Mary was an Ark of the Covenant, seeing as Jesus is the literal personification of the Covenant?
It 'could' not have happened at all; for there is NO evidence.
Yeah...
It is found in 4 John 1:1
I came back from the market with the food Mary wanted; but she was nowhere to be found..