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.

Food in the Bible generally relates to the desire for good, and drink generally relates to ideas of what is true. It makes sense then, that being hungry represents a lack of good intentions and a desire for them, while thirsting or being thirsty represents a lack of knowledge and a desire to learn what is true about life, the Lord, and what we are called to do and be.

(References: Apocalypse Explained 480; Apocalypse Revealed 381, 889, 956; Arcana Coelestia 4017, 8568)