Which day of Creation Week were the stars created?

God created the stars on the fourth day.

... And the evening and the morning were the third day. And God said: Let there be lights made in the expanse of heaven, to separate the day from the night, and let them be for signs, and for seasons, and for days and years: to shine in the firmament of heaven, and to give light upon the earth. And it was so done. And God made two great lights: a greater light to rule the day; and a lesser light to rule the night: and the stars. And he set them in the firmament of heaven to shine upon the earth. And to rule the day and the night, and to divide the light and the darkness. And God saw that it was good. And the evening and morning were the fourth day.

The first words introduce the account, to tell the reader what the account is of (namely, the creation by God of the heavens and the earth), and what follows are the specific details of the divisions and specifications of creatures within said, and the day on which they were made.

God created the stars on the fourth day. On the first day perhaps God created the matter from which other things were made. So on the first day, perhaps matter, time, and space were made, awaiting the organisation that came later, on subsequent days.

In general, we are not obligated to understand all the details of the first week of the Universe: it is enough to know that God says he created all things in six days, and to believe it because he says it. Really it is a question of whether we believe the Bible is the Word of the living God who cannot lie.

The Stars

As a Seventh-Day Adventist, I believe in a literal 6-day creation. I also believe this is what the Bible teaches. I believe that the stars, as mentioned in Genesis 1:14-19, were created on the fourth day:

14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:

15 And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.

16 And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.

17 And God set them in the firmament of the heaven to give light upon the earth,

18 And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.

19 And the evening and the morning were the fourth day.

The Heavens

The Bible references 3 "heavens". One is the atmosphere, where the birds fly; the second is where the stars, planets, and sun reside, or what we know as "space"; and the third is what is referred to as the "Third Heaven" which is where Paradise is, and where God resides:

I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth;) such an one caught up to the third heaven.

2 Corinthians 12:2

1 Kings 8 also makes mention of the 3rd heaven, which is called the heaven of heavens here:

But will God indeed dwell on the earth? behold, the heaven and heaven of heavens cannot contain thee; how much less this house that I have builded?

1 Kings 8:27

I make this differentiation, to show that Genesis 1:1 says that the heavens and the earth were created. Nevertheless, this means at least 2 heavens were created, but not necessarily all three.

Genesis 1:1

In the beginning God created the heaven and the earth.

Genesis 1:1 is a very interesting passage that we studied in Old Testament studies when I was in college.

You can take Genesis 1:1 to be part of the first day of the week of creation, which some do, and this means that God created the atmosphere (the first heaven), and space (the second heaven), along with the planets on that first day. And had already created the 3rd heaven, where He and the angels resided, also where there was a war.

And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels, and prevailed not; neither was their place found any more in heaven.

Revelation 12:7, 8

However, there is a second option. You can take Genesis 1:1 to be something that God created MUCH before creation as Genesis simply mentions "In the beginning...". When this beginning was no one really knows. It could be that The space and planets were created "in the beginning" of all creation, third heaven and angels included. Then years later (hundreds, thousands, or perhaps millions of years; no one really knows) God came back and started the week of creation in verse 2 and where He found that it was empty and void. Those who believe in this, do not necessarily believe in a young earth, but still do believe in a literal 6-day creation.

Nigel is correct in his comment that Biblical languages have a different meaning of heavens, and it is also correct that there are 3 different uses for heavens.

A better way to understand it is "Sky", "Space" and "Stratosphere", but then there is also a use of Heaven, which has the meaning of where God dwells. It's not on earth, but it's another spirit realm that's more than just the literal clouds.

As you would imagine there are countless denominations and subgroups which consider themselves as "Biblical Creationists". Anything 6000-10,000 years old is arguably ancient. The idea of referring to these as young earth creationists is a misnomer. So to be clear, I'm talking about people who believe in the literal Biblical 6 day creation account as recorded in Genesis. I've been a member of about 12 different Evangelical denominations - Independent Baptist, Bible Methodist, Nazarene, Evangelical Free Church of America, Church of God Holiness, PCA, and Church of Christ in Christian Union, and in all of these, the clear understanding and widespread belief is that as DJClayworth mentioned, planets are part of stars, and are clearly listed as being created on Day 4 of Creation.

This is very very significant point for those who hold a Literal Biblical Creation view, because it means that trees and plants were created on day 3 and the sun was created on day 4.

This is perfectly consistent with scripture that says that in Heaven there will be neither the sun nor moon, for God himself is the light. https://biblehub.com/revelation/21-23.htm Rev 21:23 "The city does not need the sun or the moon to shine on it, for the glory of God gives it light, and the Lamb is its lamp." See also Revelation 22:5 New International Version "There will be no more night. They will not need the light of a lamp or the light of the sun, for the Lord God will give them light. And they will reign for ever and ever."

The fact of the sun being created on day 4 is significant in 2 ways.

1. Because God didn't want people to worship the sun as being the source of life. [some still do worship the sun god] God wanted His people to be different. Most of the Middle Eastern people have a solar calendar, but God chose his people to use a Lunar calendar.

2. The point of the sun, moon and stars being created on day 4 is a huge dilemma for those who say that these were long eras, or 1000 year epochs- not 24 hour days, as they cannot explain how plants and trees could grow for 1000 years without the sun.

Biblical creationists believe God made the land and sky, plants and trees on day 3, and He himself is light and life according to scripture, and then created the sun, moon, stars and planets on day 4.

Of course there are exceptions within Evangelical Christianity, but this is the predominant view among most Evangelicals who hold a Literal Biblical Creation account.