Day
Like other descriptions of time in the Word, "a day" or a number of "days" describe a spiritual state rather than our natural concept of time. A spiritual "day" describes a state of mind or a state in our relationship with the Lord rather than a 12-hour or 24-hour span of natural time. "Day" describes a state in which we are turned toward the Lord, and are receiving light (which is truth) and heat (which is a desire for good) from the Lord.
Daniel 7:27
27
The kingdom and the dominion, and the greatness of the kingdoms under the whole sky, shall be given to the people of the saints of the Most High: his kingdom is an everlasting kingdom, and all dominions shall serve and obey him.
