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.

354. Internal Meaning of Psalm 104

Song in praise of the Lord. (16, 3)

1-4 From Him are Divine truths, or the Word. (16)

5-9 Of the sense of the letter of the Word, on which the church is founded: 16, (16, 11)

10-23 from this all are taught, everyone according to the state of His intelligence;, (16, 11)

24-30 from this are the knowledges [cognitiones] of truth and good, from which is spiritual nourishment 16, (16, 11)

31-35 May the good be saved, and the evil perish! (17, 11)