The atheists think that the subject of creation in 6 days is contradicted. In a verse it says ‘’I created the land and the sky and all between them in 6 days’’. Another verse says ‘’created land in two days’’. Another verse says ‘’created the sky in two days’’. Another verse says ‘’created very stable mountains and livelihood in four days’’.
They read these verses and say land was created in 2 days, the sky in 2 days and the mountains together with livelihood in 4 days, so the total is 8 days not 6. They claim this is a contradiction. In fact this is a subject that can be understood by anyone who can think. Let us explain with examples.

Let us say you are preparing dinner. There are soup, rice, meat, dessert and salad in the menu. You say you did all of them in one hour.

You say I cooked the soup in half an hour, the meat in half an hour, each of the rice, salad and dessert in 15 minutes.

It seems like you did it in one hour and 45 minutes. What do we understand from here? It means that you cooked some them simultaneously. The total took 1 hour.

Relevant Verses:

Allah; created the skies, the land and those between them in six days… (Secde Surah, 4)
Tell: “Are you really denying who created the land in two days and claiming that he has partners?… “ (Fussilet Surah, 9)
He completed them within two days as seven skies and gave his order to each sky… (Fussilet Surah, 12)
He created stable mountains on it, he created livelihood on it and granted them equally to those who ask for it in four days. (Fussilet Surah, 10)
Scientific explanation of creation in six days
The term of 6 days mentioned in the verse is not the period of a week with 1 missing day or 6 days that each consists of 24 hours. It means period. Allah is out of place and time. Everything happens at once before Allah. We are subject to time and place…

Taking into consideration the relativity of time, ‘’day’’ does not mean the period of time that consists of 24 hours in our world. But the term of ‘’day’’ is much longer in another place or time of the universe.
In these verses (Secde Surah, 4; Yunus Surah, 3; Hud Surah, 7; Furkan Surah, 59; Hadid Surah, 4; Kaf Surah, 38; Araf Surah, 54) the term of 6 days (sitteti eyyamin) in which the word “eyyamin” is used, means “days” as well as “period, era, term”.
The energy during the Big bang slowed down the flow speed of the universal time a million by million (1012) times. When the universe was created, the flow coefficient of the universal time – according to what we understand today – was a million by million times greater, which means that time was flowing faster. Therefore during living million by million minutes in the world, just one minute is passed in the universal watch.

The period of 6 days, when calculated taking into consideration the relativity of time, is equal to 6 million by million (trillion) days. Because the universal watch is a million by million times faster than the flow of the watch in the world. The number of years equivalent to 6 trillion days is approximately 16.427 billion. This number is the predicted as the age of the universe today.

6.000.000.000.000 days / 365,25 = 16.427.104.723 years

Every 6^th day of the creation – with our perception – is equivalent to different times than each other. The reason of it is that the flow coefficient of time decreases inversely proportional to the expanding of the universe.

Whenever the size of universe doubled starting from the Big bang, the flow coefficient of time decreases in half. As the universe got bigger, the doubling speed of the universe slowed down drastically.

This expanding rate, is a scientific fact known worldwide and mentioned in the textbooks of the Basis of Physical Cosmology. When we calculate each day of the creation we get the following status:
* Taking into consideration the start of time, the creation’s

1. day (1. phase) took 24 hours. But this period, is 8 billion years according to our perception of time.

* 2. Day of creation (2. phase) took 24 hours. But this period, is 4 billion years according to our perception of time which is half of the previous day.

* 3. day (3. phase) took a period equivalent to half of the 2. day. Thus, 2 billion years.

* 4. day (4. phase) 1 billion years,

* 5. day (5. phase) 500 million years,

* and 6. day (6. phase) 250 million years.

* Result: The 6^th day of creation, which is the 6^th phase, when added according to the time perception in our world, is equal to 15 billion 750 million years. This number is in parallel with the estimations done today.