Genesis 1:8

⁸ And God called the firmament Heaven. And the evening and the morning were the second day.

Three and a half

In Revelation 11:9, this signifies to the end and the beginning, or to the end of the present church and the beginning of a new church. (Apocalypse Revealed 505) It also signifies the same as a week because it is half of seven. (Apocalypse Revealed 505[2])

⁶ Thou coveredst it with the deep as with a garment: the waters stood above the mountains.