23. Nothing is more common in the Word than for the word 'day' to be used to mean the particular time at which events take place, as in Isaiah,

The day of Jehovah is near. Behold, the day of Jehovah comes. I will make heaven tremble, and the earth will be shaken out of its place, on the day of My fierce anger. Its time is close at hand, and its days will not be prolonged. Isaiah 13:6, 9, 13, 22.

And in the same prophet,

Her antiquity is in the days of antiquity. On that day Tyre will be forgotten for seventy years, like the days of one king. Isaiah 23:7, 15.

Since 'day' stands for the particular time it also stands for the state associated with that particular time, as in Jeremiah, Woe to us, for the day has declined, for the shadows of evening have lengthened! Jeremiah 6:4

And in the same prophet,

If you break My covenant that is for the day and My covenant that is for the night, so that there is neither daytime nor night at their appointed time. Jeremiah 33:20, 25.

Also,

Renew our days as of old. Lamentations 5:21.

Heaven" and "heavens" are used many times in the Bible, with a couple of variations of meaning. Sometimes it is relatively literal, including times when the Lord is identified with it (“Our Father, who art in the heavens,” for instance), meaning heaven as the eternal home for people who chose to do what is good in this life and let the Lord lead them to a love of being good. In other references, particularly when it is paired with “earth” or other lesser ideas (“In the beginning God created the heavens and the earth,” for instance), “heaven” or “heavens” means our internal life as opposed to our external life. In a way, these two meanings are really the same. If you think about the importance of your deepest thoughts and feelings, you can see that they are the “real” you, much more so than your body is. The relationship between the spiritual world and the natural world is similar; the spiritual world is the “real” one, and controls the natural world the same way our thoughts and feeling control our actions. So in both cases, “heaven” describes a deeper reality that we will enter fully after we die.