In biblical terms, the fourth watch of the night begins at 3 a.m. The four watches of the night are at three-hour intervals. The first watch begins at 6 p.m. and ends at 9 p.m.
One of the mentions of the fourth watch of the night is in Matthew 14:25 of the New Testament. In this verse, Jesus is witnessed by his disciples as having walked on the water in the sea of Galilee.
The biblical hours of the day break at sunset. This is at 6 p.m. Calendar days in modern times have the break at midnight with 12-hour days and 12-hour nights.